OTPme (https://github.com/the2nd/otpme) is an open source (GPL) authentication, directory and fileserver. It is written in python and comes with an SSO portal which supports fido2, passkeys and TOTP logins. See the (yet incomplete) Getting Started Guide on https://otpme.readthedocs.io/en/latest/ to get an overview.Its currently in alpha stage, so dont use it in production.