screen sharing?

[TheFu]

Troubleshooting ssh Connections: https://blog.jdpfu.com/2015/08/17/tr...sh-connections
ssh has to work before X11 forwarding can work.
Name resolution may or may not work. You can fix it, if you like, or ignore it using either the IP address or by setting up a ~/.ssh/config file that hides the IP from all your commands. Whatever you like.

[hmiersch]

I'll check that when I get home.

[TheFu]

I'll check that when I get home.

Hopefully, the ssh server is installed on the remote system and ssh client (CLI version) is installed on the client. The server needs to have the ssh-port used allowed through those firewall(s). Most clients allow outbound connections.

If you think there is a firewall problem, please explain the networking between the 2 systems. On the same LAN, usually means only the remote system firewall might be an issue. Obviously, if going over the internet, there will be other considerations.

[HermanAB]

Debug tip:
Test ssh on the SAME computer first. Only if that works, try it from a different networked computer:
$ ssh localhost

If the above doesn't work, then there is absolutely no way that it will work from another networked computer - so fix this problem first.