Are you able to provide some details on how you are doing this? I don’t think you can do much with reverse proxies and SSH beyond routing all traffic on port 22 (or the configured SSH port) to whichever port SSH is listening on. In other words, the reverse proxy cannot route SSH traffic for the host on port 22 to the host, route SSH traffic for Forgejo on port 22 to Forgejo’s SSH process, and SFTP traffic on port 22 to the SFTP process - at least not via domain name like a HTTP/HTTPS reverse proxy would work.
Instead, this would need to be done via IP address where the host SSH process listens on 192.168.1.2, the Forgejo SSH process listens on 192.168.1.3, and the SFTP process listens on 192.168.4. Otherwise, each of those services would need to use different ports.