You can use an OTP Generator like Aegis Authenticator from F-Droid. Afaik it even works offline, so there should be no risk if you strictly keep it offline.

Keine Lösung des Problems (darum kümmert sich vielleicht Max Schrems), aber 1ft.io gibts auch noch.

https://1ft.io/

Sounds interesting. Do you have a source for the mentioned research?