enabling 2FA with TOTP

[hlvs44]

Hallo,
how is it possibile to enable TOTP?
I find just the "issuer" parameter in config file. The instructions say "Authenticators.DomainURL: Full url of the vpn authentication endpoint, required for webauthn and oidc", not for TOTP.
Where can I input the One Time Password? Have I to set a web server for that? Is it inclueded in WAG?
Does the wag webserver generate a seed hash or a QR code for the authenticator apps when adding a user?
When I activate the connection, how can I insert a TOTP code? I don't think it's possible to do that into the wireguard-client android ufficial app, so is it needed a server to input that?
Thanks a lot.
Ale