Yes you're right, what I'm thinking of is basically a magic mirror without the mirror. Thanks for the link, I will check that out!
Vaultwarden is not compiled from Bitwarden's code, it's a separate project and codebase but designed to be compatible with Bitwarden's API.Bitwarden is open source and you can self-host it but IIRC it's a bit more complex and resource-hungry than Vaultwarden.
This looks promising, thanks!