diff --git a/keyserver/src/responders/website-responders.js b/keyserver/src/responders/website-responders.js
--- a/keyserver/src/responders/website-responders.js
+++ b/keyserver/src/responders/website-responders.js
@@ -236,10 +236,6 @@
   _persist: t.Nil,
   commServicesAccessToken: t.Nil,
   inviteLinksStore: inviteLinksStoreValidator,
-  lastCommunicatedPlatformDetails: t.irreducible(
-    'default lastCommunicatedPlatformDetails',
-    _isEqual(null),
-  ),
   keyserverStore: keyserverStoreValidator,
 });
 
@@ -606,7 +602,6 @@
     _persist: null,
     commServicesAccessToken: null,
     inviteLinksStore: inviteLinksStorePromise,
-    lastCommunicatedPlatformDetails: null,
     keyserverStore: keyserverStorePromise,
   });
   const validatedInitialReduxState = validateOutput(
diff --git a/lib/reducers/master-reducer.js b/lib/reducers/master-reducer.js
--- a/lib/reducers/master-reducer.js
+++ b/lib/reducers/master-reducer.js
@@ -9,7 +9,6 @@
 import { reduceEntryInfos } from './entry-reducer.js';
 import reduceInviteLinks from './invite-links-reducer.js';
 import reduceKeyserverStore from './keyserver-reducer.js';
-import reduceLastCommunicatedPlatformDetails from './last-communicated-platform-details-reducer.js';
 import reduceLifecycleState from './lifecycle-state-reducer.js';
 import { reduceLoadingStatuses } from './loading-reducer.js';
 import reduceNextLocalID from './local-id-reducer.js';
@@ -145,10 +144,6 @@
         action,
       ),
       inviteLinksStore: reduceInviteLinks(state.inviteLinksStore, action),
-      lastCommunicatedPlatformDetails: reduceLastCommunicatedPlatformDetails(
-        state.lastCommunicatedPlatformDetails,
-        action,
-      ),
       keyserverStore,
     },
     storeOperations: {
diff --git a/lib/types/redux-types.js b/lib/types/redux-types.js
--- a/lib/types/redux-types.js
+++ b/lib/types/redux-types.js
@@ -135,7 +135,6 @@
   +deviceToken: ?string,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
-  +lastCommunicatedPlatformDetails: ?PlatformDetails,
   +keyserverStore: KeyserverStore,
   ...
 };
diff --git a/native/redux/persist.js b/native/redux/persist.js
--- a/native/redux/persist.js
+++ b/native/redux/persist.js
@@ -757,6 +757,23 @@
       actualizedCalendarQuery,
     };
   },
+  [51]: async state => {
+    const { lastCommunicatedPlatformDetails, keyserverStore, ...rest } = state;
+
+    return {
+      ...rest,
+      keyserverStore: {
+        ...keyserverStore,
+        keyserverInfos: {
+          ...keyserverStore.keyserverInfos,
+          [ashoatKeyserverID]: {
+            ...keyserverStore.keyserverInfos[ashoatKeyserverID],
+            lastCommunicatedPlatformDetails,
+          },
+        },
+      },
+    };
+  },
 };
 
 // After migration 31, we'll no longer want to persist `messageStore.messages`
@@ -888,7 +905,7 @@
     'connection',
   ],
   debug: __DEV__,
-  version: 50,
+  version: 51,
   transforms: [
     messageStoreMessagesBlocklistTransform,
     reportStoreTransform,
diff --git a/native/redux/redux-setup.js b/native/redux/redux-setup.js
--- a/native/redux/redux-setup.js
+++ b/native/redux/redux-setup.js
@@ -120,7 +120,6 @@
   inviteLinksStore: {
     links: {},
   },
-  lastCommunicatedPlatformDetails: null,
   keyserverStore: {
     keyserverInfos: {
       [ashoatKeyserverID]: {
diff --git a/native/redux/state-types.js b/native/redux/state-types.js
--- a/native/redux/state-types.js
+++ b/native/redux/state-types.js
@@ -3,7 +3,6 @@
 import type { Orientations } from 'react-native-orientation-locker';
 import type { PersistState } from 'redux-persist/es/types.js';
 
-import type { PlatformDetails } from 'lib/types/device-types.js';
 import type { DraftStore } from 'lib/types/draft-types.js';
 import type { EnabledApps } from 'lib/types/enabled-apps.js';
 import type { EntryStore, CalendarQuery } from 'lib/types/entry-types.js';
@@ -56,6 +55,5 @@
   +userPolicies: UserPolicies,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
-  +lastCommunicatedPlatformDetails: ?PlatformDetails,
   +keyserverStore: KeyserverStore,
 };
diff --git a/web/redux/persist.js b/web/redux/persist.js
--- a/web/redux/persist.js
+++ b/web/redux/persist.js
@@ -27,6 +27,7 @@
   generateIDSchemaMigrationOpsForDrafts,
   convertDraftStoreToNewIDSchema,
 } from 'lib/utils/migration-utils.js';
+import { ashoatKeyserverID } from 'lib/utils/validation-utils.js';
 
 import commReduxStorageEngine from './comm-redux-storage-engine.js';
 import type { AppState } from './redux-setup.js';
@@ -107,6 +108,23 @@
 
     return newState;
   },
+  [4]: async state => {
+    const { lastCommunicatedPlatformDetails, keyserverStore, ...rest } = state;
+
+    return {
+      ...rest,
+      keyserverStore: {
+        ...keyserverStore,
+        keyserverInfos: {
+          ...keyserverStore.keyserverInfos,
+          [ashoatKeyserverID]: {
+            ...keyserverStore.keyserverInfos[ashoatKeyserverID],
+            lastCommunicatedPlatformDetails,
+          },
+        },
+      },
+    };
+  },
 };
 
 const persistWhitelist = [
@@ -115,7 +133,6 @@
   'cryptoStore',
   'notifPermissionAlertInfo',
   'commServicesAccessToken',
-  'lastCommunicatedPlatformDetails',
   'keyserverStore',
 ];
 
@@ -195,7 +212,7 @@
     { debug: isDev },
     migrateStorageToSQLite,
   ): any),
-  version: 3,
+  version: 4,
   transforms: [keyserverStoreTransform],
 };
 
diff --git a/web/redux/redux-setup.js b/web/redux/redux-setup.js
--- a/web/redux/redux-setup.js
+++ b/web/redux/redux-setup.js
@@ -18,7 +18,6 @@
   OLMIdentityKeys,
   PickledOLMAccount,
 } from 'lib/types/crypto-types.js';
-import type { PlatformDetails } from 'lib/types/device-types.js';
 import type { DraftStore } from 'lib/types/draft-types.js';
 import type { EnabledApps } from 'lib/types/enabled-apps.js';
 import type { EntryStore, CalendarQuery } from 'lib/types/entry-types.js';
@@ -95,7 +94,6 @@
   +_persist: ?PersistState,
   +commServicesAccessToken: ?string,
   +inviteLinksStore: InviteLinksStore,
-  +lastCommunicatedPlatformDetails: ?PlatformDetails,
   +keyserverStore: KeyserverStore,
 };