diff --git a/addons/mail/static/src/scss/systray.scss b/addons/mail/static/src/scss/systray.scss
index 66ef3d273aa..9a46d099928 100644
--- a/addons/mail/static/src/scss/systray.scss
+++ b/addons/mail/static/src/scss/systray.scss
@@ -111,7 +111,16 @@
             top: 10%;
         }
         .o_mail_systray_dropdown {
-            position: relative;
+
+            position: fixed;
+            top: $o-mail-chat-window-header-height-mobile;
+            bottom: 0;
+            left: 0;
+            right: 0;
+            width: map-get($sizes, 100);
+            margin: 0;
+            max-height: none;
+
             .o_mail_systray_dropdown_top {
                 padding: 5px;
             }
diff --git a/addons/web/static/src/core/dropdown/dropdown.scss b/addons/web/static/src/core/dropdown/dropdown.scss
index ebd3bffa123..4093ec49ebd 100644
--- a/addons/web/static/src/core/dropdown/dropdown.scss
+++ b/addons/web/static/src/core/dropdown/dropdown.scss
@@ -68,21 +68,14 @@
   &_menu {
     @extend .dropdown-menu;
 
-    &.o_dropdown_menu_right {
-      // FIXME: does commenting this break anything?
-      // @extend .dropdown-menu-right;
-    }
-
     & > li.o_dropdown {
       &.focus > .o_dropdown_toggler {
         background-color: $dropdown-link-hover-bg;
       }
       & > .o_dropdown_toggler {
-        // FIXME: without this there is no selection feedback
-        // @extend .dropdown-item;
         &:after {
-          @include o-position-absolute($right: 0);
-          transform: translate(-.6em, .3em);
+          @include o-position-absolute($right: 0, $top: 0);
+          transform: translate(-.6em, .6em);
           font: .9em/1em FontAwesome;
           content: "\f0da";
         }
@@ -122,90 +115,11 @@
     }
   }
 
-  &_item > *:first-child:last-child {
-    @extend .dropdown-item;
-  }
-
-  &_item.o_dropdown_active > *:first-child:last-child {
-    @extend .dropdown-item:hover;
-  }
-
   &_menu_group {
     @extend .dropdown-header;
   }
 }
 
-// = Owl Nested Dropdowns
-// ----------------------------------------------------------------------------
-
-.o_dropdown .o_dropdown {
-
-  // Define submenus 'inline' design (nested into the parent menu)
-  @mixin -o-inline-dropdown-menu {
-    .o_dropdown_toggler.o_dropdown_active:after {
-      content: "\f0d7";
-    }
-
-    .o_dropdown_menu {
-      left: 0;
-      position: relative;
-      max-height: none;
-      box-shadow: none;
-      margin-top: 0;
-      margin-bottom: $dropdown-padding-y;
-      padding-top: 0;
-      background: rgba(#000, .01);
-      border-width: 0 0 1px 0;
-
-      &:last-child {
-        border-bottom-width: 0;
-        margin-bottom: 0;
-      }
-    }
-  }
-
-  // The toggler looks like a regular menu entry
-  .o_dropdown_toggler {
-    @extend .dropdown-item;
-
-    &:after {
-      @include o-position-absolute($right: 0);
-      transform: translate(-.6em, .3em);
-      font: .9em/1em FontAwesome;
-      content: "\f0da";
-    }
-  }
-
-  // Small screen: all submenus are inline
-  @include media-breakpoint-down('lg') {
-    @include -o-inline-dropdown-menu ;
-  }
-
-  // Large screen: submenus floats...
-  @include media-breakpoint-up('lg') {
-    .o_dropdown_menu {
-      top: 0;
-      left: 100%;
-    }
-
-    //... except when specified otherwise
-    &.o_dropdown_inline {
-      @include -o-inline-dropdown-menu ;
-    }
-  }
-}
-
-// Unfortunately is not possible to set the parent menu's overflow to be 'visible'
-// horizontally (to show floating submenus) and 'auto/scroll' vertically (to hide
-// menu entries when the menu is very long).
-// We will set it 'visible' letting 'o_view_controller' handling scrollbars.
-@include media-breakpoint-up('lg') {
-  .o_dropdown_menu {
-    overflow: visible;
-    max-height: none;
-  }
-}
-
 // = Owl components specific rules
 // -----------------------------------------------------------------------------
 .o_dropdown_item:not(.disabled):not(:disabled) {
@@ -224,10 +138,6 @@ button.o_dropdown_toggler {
     box-shadow: none !important;
   }
 
-  &.o_dropdown_active {
-    @extend %--state-active;
-  }
-
   @include hover-focus-active() {
     @extend %--state-active;
   }
diff --git a/addons/web/static/src/core/dropdown/dropdown.xml b/addons/web/static/src/core/dropdown/dropdown.xml
index 525c5b66317..48c33d17f38 100644
--- a/addons/web/static/src/core/dropdown/dropdown.xml
+++ b/addons/web/static/src/core/dropdown/dropdown.xml
@@ -17,7 +17,7 @@
         t-att-data-hotkey="props.hotkey"
         t-ref="togglerRef"
       >
-        <span>
+        <span class="d-flex align-items-center">
           <t t-slot="toggler" />
         </span>
       </button>
diff --git a/addons/web/static/src/search/comparison_menu/comparison_menu.xml b/addons/web/static/src/search/comparison_menu/comparison_menu.xml
index 0c676e49ee8..afe62a61554 100644
--- a/addons/web/static/src/search/comparison_menu/comparison_menu.xml
+++ b/addons/web/static/src/search/comparison_menu/comparison_menu.xml
@@ -2,12 +2,12 @@
 <templates xml:space="preserve">
 
     <t t-name="web.ComparisonMenu" owl="1">
-        <Dropdown class="o_comparison_menu"
+        <Dropdown class="o_comparison_menu btn-group"
             togglerClass="'btn btn-secondary'"
             t-on-dropdown-item-selected="onComparisonSelected"
             >
             <t t-set-slot="toggler">
-                <i class="mr-1" t-att-class="icon"/>
+                <i class="small mr-1" t-att-class="icon"/>
                 <span class="o_dropdown_title">Comparison</span>
             </t>
             <t t-foreach="items" t-as="item" t-key="item.id">
diff --git a/addons/web/static/src/search/favorite_menu/favorite_menu.xml b/addons/web/static/src/search/favorite_menu/favorite_menu.xml
index 690925e8cc4..4631765e594 100644
--- a/addons/web/static/src/search/favorite_menu/favorite_menu.xml
+++ b/addons/web/static/src/search/favorite_menu/favorite_menu.xml
@@ -2,12 +2,12 @@
 <templates xml:space="preserve">
 
     <t t-name="web.FavoriteMenu" owl="1">
-        <Dropdown class="o_favorite_menu"
+        <Dropdown class="o_favorite_menu btn-group"
             togglerClass="'btn btn-secondary'"
             t-on-dropdown-item-selected="onFavoriteSelected"
             >
             <t t-set-slot="toggler">
-                <i class="mr-1" t-att-class="icon"/>
+                <i class="small mr-1" t-att-class="icon"/>
                 <span class="o_dropdown_title">Favorites</span>
             </t>
             <t t-set="currentGroup" t-value="null"/>
diff --git a/addons/web/static/src/search/filter_menu/filter_menu.xml b/addons/web/static/src/search/filter_menu/filter_menu.xml
index f562887e5cf..a3fe871b295 100644
--- a/addons/web/static/src/search/filter_menu/filter_menu.xml
+++ b/addons/web/static/src/search/filter_menu/filter_menu.xml
@@ -2,12 +2,12 @@
 <templates xml:space="preserve">
 
     <t t-name="web.FilterMenu" owl="1">
-        <Dropdown class="o_filter_menu"
+        <Dropdown class="o_filter_menu btn-group"
             togglerClass="'btn btn-secondary'"
             t-on-dropdown-item-selected="onFilterSelected"
             >
             <t t-set-slot="toggler">
-                <i class="mr-1" t-att-class="icon"/>
+                <i class="small mr-1" t-att-class="icon"/>
                 <span class="o_dropdown_title">Filters</span>
             </t>
             <t t-set="currentGroup" t-value="null"/>
diff --git a/addons/web/static/src/search/group_by_menu/group_by_menu.xml b/addons/web/static/src/search/group_by_menu/group_by_menu.xml
index 384a15337a4..d990950a320 100644
--- a/addons/web/static/src/search/group_by_menu/group_by_menu.xml
+++ b/addons/web/static/src/search/group_by_menu/group_by_menu.xml
@@ -2,13 +2,13 @@
 <templates xml:space="preserve">
 
     <t t-name="web.GroupByMenu" owl="1">
-        <Dropdown class="o_group_by_menu"
+        <Dropdown class="o_group_by_menu btn-group"
             togglerClass="'btn btn-secondary'"
             t-props="dropdownProps"
             t-on-dropdown-item-selected="onGroupBySelected"
             >
             <t t-set-slot="toggler">
-                <i class="mr-1" t-att-class="icon"/>
+                <i class="small mr-1" t-att-class="icon"/>
                 <span class="o_dropdown_title">Group By</span>
             </t>
             <t t-set="currentGroup" t-value="null"/>
diff --git a/addons/web/static/src/webclient/navbar/navbar.xml b/addons/web/static/src/webclient/navbar/navbar.xml
index 11b3fe0d3f9..6f3bfa8d797 100644
--- a/addons/web/static/src/webclient/navbar/navbar.xml
+++ b/addons/web/static/src/webclient/navbar/navbar.xml
@@ -52,7 +52,7 @@
         t-as="app"
         t-key="app.id"
         class="o_app"
-        t-att-class="{ o_dropdown_active: menuService.getCurrentApp() === app }"
+        t-att-class="{ focus: menuService.getCurrentApp() === app }"
         payload="app"
       >
         <a t-att-href="getMenuItemHref(app)" t-esc="app.name" t-on-click.prevent="" />
diff --git a/addons/web/static/tests/core/dropdown_tests.js b/addons/web/static/tests/core/dropdown_tests.js
index c6d1f5b8a3d..8491e09c0ea 100644
--- a/addons/web/static/tests/core/dropdown_tests.js
+++ b/addons/web/static/tests/core/dropdown_tests.js
@@ -42,7 +42,7 @@ QUnit.module("Components", ({ beforeEach }) => {
         parent = await mount(Parent, { env, target });
         assert.strictEqual(
             parent.el.outerHTML,
-            '<div class="o_dropdown"><button class="o_dropdown_toggler "><span></span></button></div>'
+            '<div class="o_dropdown"><button class="o_dropdown_toggler "><span class="d-flex align-items-center"></span></button></div>'
         );
         assert.containsOnce(parent.el, "button.o_dropdown_toggler");
         assert.containsNone(parent.el, "ul.o_dropdown_menu");
@@ -55,7 +55,7 @@ QUnit.module("Components", ({ beforeEach }) => {
         parent = await mount(Parent, { env, target });
         assert.strictEqual(
             parent.el.outerHTML,
-            '<ged class="o_dropdown"><button class="o_dropdown_toggler "><span></span></button></ged>'
+            '<ged class="o_dropdown"><button class="o_dropdown_toggler "><span class="d-flex align-items-center"></span></button></ged>'
         );
         assert.containsOnce(parent.el, "button.o_dropdown_toggler");
         assert.containsNone(parent.el, "ul.o_dropdown_menu");
diff --git a/addons/web/static/tests/webclient/navbar_tests.js b/addons/web/static/tests/webclient/navbar_tests.js
index 911a3a459ff..07d39d6a452 100644
--- a/addons/web/static/tests/webclient/navbar_tests.js
+++ b/addons/web/static/tests/webclient/navbar_tests.js
@@ -120,7 +120,7 @@ QUnit.test("navbar can display current active app", async (assert) => {
     await click(dropdown, "button.o_dropdown_toggler");
     assert.containsOnce(
         dropdown,
-        "ul.o_dropdown_menu li.o_dropdown_item:not(.o_dropdown_active)",
+        "ul.o_dropdown_menu li.o_dropdown_item:not(.focus)",
         "should not show the current active app as the menus service has not loaded an app yet"
     );
 
@@ -129,7 +129,7 @@ QUnit.test("navbar can display current active app", async (assert) => {
     await nextTick();
     assert.containsOnce(
         dropdown,
-        "ul.o_dropdown_menu li.o_dropdown_item.o_dropdown_active",
+        "ul.o_dropdown_menu li.o_dropdown_item.focus",
         "should show the current active app"
     );
     navbar.destroy();