Bitwarden supports to host the server via Docker. This is nice. But in reality a lot of people do live in a family with others. A very easy solution would be to simply run SyncThing on a NAS or even a RPi3 and simply have a 2-way sync (which is exactly the core functionality SyncThing is king of) with a folder on your nas (for each user in your household) and the Bitwarden db folder on your mobile device.
There have been other topics requesting features to support WebDAV to enable the use of NextCloud but I agree with the developers this method opens up a dark hole of conflicts.
SyncThing is different, although it can support one way sync, it excels at keeping each and every device fully in sync given a specific folder.
I am seriously considering switching from Enpass to Bitwarden and I am curious if what I am describing would work already: Constantly syncing the Bitwarden db folder on Android with Bitwarden for Windows/Firefox and/or other Android devices.
Links to SyncThing documentation for reference: default syncing method versus receive only/send only.
SyncThing syncing process p2p.
Edit: since Bitwarden server via Docker requires x86, this could be a perfect solution for personal use on a lightweight ARM based device like a Raspberry.