It could be that the app hasn’t been packaged by nix yet, but I’d find that hard to believe and more likely that I just don’t know which of these nix package yubikey search-results contains the app I’m looking for.
doh. it’s the yubioath-flutter package; writing out my question made me realize I was searching for yubikey but maybe it’s only listed under yubico… and sure enough. Kind of dissapointed there’s not some metadata that caused the app to show up for yubikey keyword, but … whatever.