When using OpenSSL 3.0.0alpha6, OpenSSH versions > 8.2p1 fail to connect anywhere, usually resulting in a "protocol error" while establishing the connection.

Bisecting OpenSSH shows this commit is what triggers the breakage:
openssh/openssh-portable@abe2b24

Defining HAVE_BROKEN_CHACHA20 in openbsd-compat/openssl-compat.h (like the openssh commit does for some versions of LibreSSL) "fixes" the problem.

Looks like EVP_chacha20 doesn't work as expected by OpenSSH.