Since I can’t edit my original post, I will write some very important information here:
Since OnlyKey doesn’t have a secure element, the longest possible PIN combination is only 10 digits, which is not enough entropy for secure encryption. Combined with the horrific software situation, it’s not something that I could personally recommend anymore.
While Nitrokey 3 has a secure element and encrypts some secrets against the PIN, passkeys and FIDO2 credentials are not stored in that secure element and aren’t encrypted against the PIN either. Combined with no potting, this is not good.
It looks like YubiKeys are still the best option for most people and for those who don’t want to spend too much.
If you’re someone who can spare €129 for an authenticator/crypto wallet, then the Trezor Safe 5 looks like the best option, beating even the YubiKeys.