How do I list available host key algorithms for an SSH client?

ssh -Q key

Unless you have an ancient version of OpenSSH, in which case uhhhh source dive, or run ssh -v -v -v ... and see if what you want appears there.

from the ssh_config manual page:

HostKeyAlgorithms
             Specifies the protocol version 2 host key algorithms that the client wants to use in order of preference.  The default for this option is:

                [email protected],
                [email protected],
                [email protected],
                [email protected],[email protected],
                [email protected],[email protected],
                ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
                ssh-rsa,ssh-dss

             If hostkeys are known for the destination host then this default is modified to prefer their algorithms.