Please can you confirm you are using https and not http - https://your_server_ip:81. You will get a browser warning in Firefox and you will have to accept the the default certificate. I believe Brave won't work as it will not allow a self-signed certificate.

Be wary of manipulating the firewall manually. At some point ClearOS will overwrite anything you do. I suggest you restart it with a "systemctl restart firewall". This will reset it and, by default it should be open on ports 22 and 81.