I use kanidm because the footprint is lower than the alternatives you mention, and it’s written in Rust.

Vautlwarden as a service is great and since it’s GPLv3 licensed there’s no way that can be shut down. But the client is another matter and maybe that doesn’t stay open for using it with Vaultwarden forever https://www.osnews.com/story/145029/get-your-passwords-out-of-bitwarden-while-you-still-can/