Cannot control SSH access to the Gaia machine with the Host IP Address, but it can control access to the Gaia Portal.
[Gaia Portal] System Management < Host Access < Add Host IP Address.
Other clients are still able to connect, but logins fail because there are no available authentication methods.
CLI access through Gaia Portal may also work and /var/log/secure will have the following lines:
User root from x.x.x.x not allowed because listed in DenyUsers
Connection closed by invalid user root x.x.x.x port yyyy [preauth]
In R80.40, Open SSH deprecated the use of tcp-wrappers (hosts.allow/hosts.deny files) in sshd itself.