Keepass does not provide anything to sync passwords between devices which seems to be an important part of Lockbox.
KeePass has a feature to sync two files, and can access a variety of network storages. That's not one turn-key solution, but it covers just about everything. Meanwhile I simply store the file in my Dropbox because I don't do concurrent edits and it's slightly more convenient that way
Honest question, but pushing your KeepassXC db into Dropbox shouldn't raise some red flags from a security perspective ? If "somebody" gets your encrypted db, they can rainbowtable the crap out of it to unlock it.
To me it seems by using Dropbox you just add another sizeable attack surface.
I would be comfortable hosting my password file publicly. Any benefits from Dropbox authentication are just defense in depth (and privacy benefits).
The DB attack surface is to some extend expected to be eventually obtained by an attacker. As long as your master password is nice and long, they "can't do shit" for a long long long while.