Thank you for chiming in.

> We have to use some kind of attestation mechanism per the eIDAS implementing acts.

What does this attestation need to prove? Is this only about ensuring that private keys are managed by a secure enclave or a TPM?

> we have support for other OSs on our list (like, e.g., GrapheneOS)

I appreciate that, even though I am really not enthusiastic of eIDAS. But time will tell. Thank you.

They won't implement alternatives later, they'll be no point if "most of out customers is using either of the major providers".

Concerning secure enclave - what other device except iphones and Pixels have it actually safe?