I recently had to downgrade gnupg to 2.3.6 after an update because it stopped working with my YubiKey:
Aug 31 11:45:58 gpg-agent[40089]: scdaemon[40089]: detected reader 'Yubico YubiKey OTP+FIDO+CCID 00 00' Aug 31 11:45:58 gpg-agent[40089]: scdaemon[40089]: DBG: Curve with OID not supported: 2b06010401da470f01 Aug 31 11:45:58 gpg-agent[40089]: scdaemon[40089]: no supported card application found: Card error
2b06010401da470f01 seems to be an OID for Ed25519 curve.
this is my config:
nazarewk@nazarewk-krul ~ % cat ~/.gnupg/scdaemon.conf pcsc-shared # disable-ccid to make YubiKey work # - https://support.yubico.com/hc/en-us/articles/360013714479-Troubleshooting-Issues-with-GPG # - https://dev.gnupg.org/T5451 disable-ccid # PIN caching fix # - https://github.com/drduh/YubiKey-Guide/issues/135 # - https://dev.gnupg.org/T3362 # fix from https://dev.gnupg.org/T5436#148656 disable-application piv nazarewk@nazarewk-krul ~ % cat ~/.gnupg/gpg-agent.conf pinentry-program /nix/store/0y1vlxssvxv4j3q922n8mjwayihvqyh9-pinentry/bin/pinentry