Seems like I’ve found the culprit: https://github.com/Magisk-Modules-Alt-Repo/trichromelibrary-squoosh

When I deactivate this module and try again, the error message disappears and shows up again when enabled.

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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.

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