Keepass2Android handles that pretty well. It checks for external changes to the remote database before every local edit. And the desktop nextcloud app notices conflicts as well and can create a second version of the file if there are conflicts. You can then check for the differences with something like keepass-diff. But that should only happen if you change your db without syncing first, so while you are offline or the nextcloud app wasn't running.
Keepass2Android implements syncing in a way that actually works. I sync through my nextcloud instance. On my laptop it's just KeepassXC and the nextcloud desktop app, on my mobile (android) devices Keepass2Android. On iOS I think there was Strongbox but I haven't used it in a long time.
I tried using KeepassDX with the nextcloud android app for syncing for a while, but it lead to regular silent sync conflicts including password losses.
I'm glad you don't have to go through Amazon anymore (or google for that matter). I think Patreon is a much better option.