Sure, but there's a big difference between a vault copied and synced on all of my mobile devices that I could easily lose versus only on a server behind locked doors.

It can generate TOTP codes, but I'm saying that the vault itself can't be secured with TOTP.

I use a KeePassXC database on a syncthing share and haven't had any issues. You get synchronization and offline access, and even if there are sync conflicts, the app can merge the two files.

One benefit to hosted password vaults over files is that they can use 2FA - you can't exactly do TOTP with a static file.

(As an aside, I wish more "self hosted" apps were instead "local file and sync friendly" apps instead, exactly because of offline access)