Git has supported SSH-based signatures for a while now, including those backed by FIDO hardware keys.

FIDO would be for authentication, not signing. It also supports SSH (and X.509, see <https://git-scm.com/docs/gitformat-signature>) but it does not support minisign or signify. There's a git module for signify, <https://leahneukirchen.org/dotfiles/bin/git-signify> but don't count on it being widely supported.