Gitlab? No. Github? No. My gateway with a hand built gentoo kernel? Yes.
It seems functional, but you've also got to be aware that `ed25519-sk` and `ecdsa-sk` have sort of spotty support in the devices too. `ed25519-sk` does not work on a Yubikey <5, for example.
Ubuntu 20.04 and later supports this, and, since that's LTS, it means that quite a few servers and machines will be supporting it already.
Github/Gitlab aren't supporting it yet, but given how great it is for security, I think they have a big incentive to speed up support.
> ed25519-ek does not work on a Yubikey <5, for example.
That's no problem, since you can just generate an ECDSA key instead, but yes, not all keys have hardware support for all algorithms.
I can SSH to my AP, my home router, all routers at basically any ISP. None of those support this. Most of them probably never will, until they're thrown away and new ones bought in 5-10 years.
Bottom line: This can't be your only key. So why bother? Why not use PIV mode/smartcard/other, which does work with every single one of these billions of devices, because they have no server-side requirements like these.
Another tradeoff. Some users may be using a cheap or old token (without PIV support) or a token with a private key slot already used for something else. Now, with a software-only upgrade (on both SSH client and server), they can user their existing token for SSH authentication.