Aftermost8040
You don't need to disable WebAuthn, If you have several second factor methods, normally you can choose the secondary method instead of WebAuthn. Just use the TOTP, log in, and remove the TOTP. I don't think removing a second factor method disconnects sessions.
It's also possible, as nrt says, to install and uninstall play services, but if you don't want them at all, I think you will have to go through the TOTP.