@David-Healey Yes. The only reason I purchased the YubiKey was to use the certs from SSL.com. However, they kept issuing incompatible certs, not for YubiKey, for what I could tell. There are two places that apparently offer downloads on their website...and they may not be the same...a shitshow.
Fun fact: after I purchased the certs from SSL.com, I watched a YouTube video on how to obtain them and install them on a YubiKey by a guy who said he spent a month and a half trying to get them to work. I thought: That's insane, what an incredibly patient person. And here we are, a month and a half later!