Does the sequoia CLI have support for smartcards like yubikeys? I checked the issue tracker and didn't see any information.
An advantage of a open and well documented offline cryptography standard. You can do stuff like that.
I mean any implementation can handle the signing etc, as the operations are an open standard. But running the actual pgp implementation on a system you have no access to sources, can't really see the advantage of just using an old laptop to have truly airgapped system (plugging your proprietary device on a connected computer doesn't look that airgapped to me)