There are keepass android apps like KeePassDX. You can have server sync with WebDav, but I don't know about shared databases. Should work if you configure the WebDav server etc.
A friend of mine is a big fan of bitwarden but I have no Idea if that fits your requirement. Should have a webui tho.
See if you can install LineageOS on it. Replaces all the dog shit and has opt in for the google services etc. if you value your privacy.
-sent from Xiaomi 11