Given the timing, I wonder if https://techcrunch.com/2021/09/21/lets-encrypt-root-expiry/ might be the cause: We serve a pretty complete certificate chain but if your client doesn't support the root certificate that we now rely on exclusively (because the other path using the more popular root has expired), your client won't like any of our certs.

You could try changing the environment to carry GIT_CURL_VERBOSE=true to see what's going on, or maybe just look at updating the ca-certificate store of your system.

Alternatively you could set up the SSH based access method to access the server, as outlined in https://doc.coreboot.org/tutorial/part2.html#step-2a-set-up-rsa-private-public-key but you might run into more issues with certs going forward on other servers if the cert store is old.

All the best,

Patrick