Why use gpg at all? SSH supports FIDO.
And of course once you do fido, you're back to the same issues around SSH keys that certificates are a solution to (as the article demonstrates). So moving to Fido is not a whole lot better than using SSH keys which work very well everywhere.
Also, another important point: I also use GPG a lot to encrypt files. It's great to use the same key (sometimes, for sensitive stuff I use a different OpenPGP card) and toolchain (always) for this. So I need it anyway, might as well use it for SSH authentication as well.
It works quite nicely, but the PIN has to be entered every time I auth to SSH. This may be a desirable feature to some, but I prefer the GPG way of the PIN being cached until the key is removed from the system.
(This could possibly be a shortcoming of KWallet, as it would pop up the dialog asking for the PIN, but checking the "remember this password" would achieve absolutely nothing, and besides, I wouldn't want to save it permanently, which that checkbox would otherwise do.)
I want GPG to ask for the pincode once, and the yubikey to require a physical touch for each authentication (including the first, obviously). This way it can't be automated by malware either (a pincode can be sniffed and replayed through the keyboard driver, the physical touch can't).
The PIN is great against attackers that find your key on the street. Not against a determined attacker that is already on your computer. For that the physical touch thing is a great solution (though the yubikey doesn't require it by default, you can easily turn it on).
Asking the pin upon first use and a touch every time is the perfect compromise between security and usability IMO. There's still some weakness around attackers with physical access but they are more easily mitigated.
OpenSSH supports FIDO2 passwordless mode natively in the latest versions.