I suppose they might want to stop issuing client auth certificates because it means anyone with a PKI-signed cert could potentially authenticate as a client to

I suppose they might want to stop issuing client auth certificates because it means anyone with a PKI-signed cert could potentially authenticate as a client to a server. With PKI being a series of trust relationships among CAs, there's effectively no control over what gets accepted vs. rejected. I suppose from that perspective only private CAs make sense. If you want to try using a private CA for x509 certificates to do SSH client authentication, I know of a couple solutions that make it easy to do: Smallstep: https://smallstep.com/docs/tutorials/ssh-certificate-login/ https://smallstep.com/docs/tutorials/ssh-certificate-login/ Infiniscal: https://infisical.com/docs/documentation/platform/ssh/overview https://infisical.com/docs/documentation/platform/ssh/overvi... You can also do it the hard way. For example, here's how it can be done to SSH into Cisco network gear: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9500/software/release/17-14/configuration_guide/sec/b_1714_sec_9500_cg/x_509v3_certificates_for_ssh_authentication.html https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9...