Keychain and safari tabs are not working under iOS 15

[Schultes48]

After visiting an Apple Store and contacting Apple care they could not find the reason why the keychain slider can't be set and the safari tabs are not syncing on one iPhone X and two iPad 3 gen. Several resets & login / logout safari and iCloud did not work. Other Syncs work on all other items like notes or addresses e.g.
Funnily - The problem is not existing on a old MacBook Pro 2016 and a iPhone 6s - all items mentioned are connected to the very same Apple ID.
Apple Care filed report after having looked at my iPhone over the net - anyone else encountering the same problem?

 

[dliwski]

Same here. iPhone X, iPad mini 5 and MacBook Pro 2017 (iOS 15 and Mojave) - can't disable keychain (goes on immediately after switching off). Sync works between iPad and MBP. iPhone X does not sync new passwords and has some problems with HomeKit. Even restoring iOS did not help.