I've used KeepassXC + Syncthing for about 8 years now, and it works fantastically. Syncthing provides redundancy, syncing, and versioned backups. There's a merge function with conflict resolution in KeepassXC on the off chance two copies get out of sync with each other after a long period without connectivity. I have full control over where my data resides, and the source code of the entire stack.
The only other stack I've used is on-premises Bitwarden for small businesses, because it provides a more flexible multi-user permissions model. That can be made fully self-hosted and open source by using Vaultwarden for the server.
I don't see any advantages to using Proton Pass over those, frankly.