Keepass now supports 2fa tokens, just use that. Plenty of open source clients on different platforms and you can sync the encrypted database file using whatever mechanism you like, drop box, one drive, etc.
KeepassXC (Linux) can import Bitwarden files directly as well, as both programs support H/TOTP there's a solution here. Not what I do, but I can see the use case aligning to the GP's comment - using Bitwarden (e.g.) as the TOTP app could allow importing it's backups to KeepassXC if your main/only mobile device fails and you only have a laptop etc.
