Just reread what you meant, yeah, I see that self-signing wouldn't neccesarilly solve the issue. As you say, it might also be that some apps use root status. After they updated our digital signing platform, a colleague who had a phone from china which wasn't even that old, stopped working, and I've had friends which had the same thing happen. They weren't rooted. So I don't know if there is some hardware component to it, like TPM that you mentioned? It's worth saying, you cannot use banking apps here, without a valid digital signature, which proofs your identity. It's not just the financial app itself, it's the legal requirements we have here, which make the financial apps use this digital identity verification.

So if self signing cannot guarantee those assumptions that are being made, there's no way around it.