The only thing I can think of is that no smartcard/usb-key that I know of suppor...

amaccuish · on Aug 4, 2018

The OpenPGP 3.3 card has ECC but not Ed25519 :(

FYI it supports [0]: ansix9p256r1, ansix9p384r1, ansix9p521r1 and brainpoolP256r1, brainpoolP384r1, brainpoolP512r1

[0] https://gnupg.org/ftp/specs/OpenPGP-smart-card-application-3...

wahern · on Aug 3, 2018

I think some OpenPGP smartcards like the GnuK might support it, but no PIV mode cards AFAIK. And I don't know if the components higher up the stack (gpg-agent, ssh-agent, PKCS#11 drivers, etc) can make use of those keys. Each new key type requires protocol support up and down the stack.