With Bitwarden, I cannot create a new password or change existing one without being online, but I consider that a small price for not having to deal with conflicts anymore.
I assumed people would switch from Keepass + database synced on a private server to something else when they started working in teams and need better/easier permission models. :)
As you have mentioned it, I have written the tool keepass-diff (<https://github.com/Narigo/keepass-diff/>) to help me for exactly these conflicts and I could quickly resolve the issues with it. It was still useful enough to let me keep using Keepass. Was it not working for you or was it too hard to use because of how it needs to be set up first? Would you have stayed with Keepass + sync if something similar to this was integrated into UI clients?
Not sure if NextCloud could be causing some issues? As I mentioned, I believe Seafile automatically overwrites (to newest version) and it's been fine (there's history if you lose something, which shouldn't happen anyway).
I do think this merge functionality would be very nice in KPXC, but for other reasons: I sometimes use the browser databases to save passwords (when I forget to open KP) and I need to merge the new entires.
Yet, the sync conflicts happened anyways. The first time it was quite shock, why my password doesn't work, but then I found the conflict password file and the password from there worked.
Your tool made it much easier, big thanks for creating it.
Maybe, if the keepassxc had in the UI, that it detected a sync conflict (that would involve a knowledge how the misc sync tools work) and offered merging them, I would probably stayed.
Ultimately, I switched to vaultwarden, on the same above-mentioned NAS. It does not have all the features of the keepassxc, but it is good enough for me, the sync problems disappeared, and the browser integration works a little bit better (doesn't complain that the main app isn't running, while it is).