As already mentioned in a comment for SiskinIM, in most scenarios you should not be using server name or need to specify server name to connect to the XMPP server, see https://github.com/tigase/siskin-im/issues/23#issuecomment-604664615

But my boss has hosted the server on our local network.

192.168.1.225

So I need to point the server address and port.

You can have DNS SRV entries resolving to local IP addresses, so there is still no need for setting custom server name.

Thanks. I resolved that. But one more question. How can I group the contacts?

I suppose you are referring to the grouping of contacts in the contacts window. That is not supported.

Okay, then is this feature in your future roadmap or not in your next plans?

It is not on the roadmap as we are trying to remove the requirement for people to use the contacts window and allow them to chat from the chats window.

I tried to make the font bigger or smaller, but it's not working.

If you are referring to the top bar "Format" menu, then it is not working as it is not supported and that will be fixed by removal of that menu.

Oh no, can you please add that feature in the next release? Font Size, or Zoom In & Out.

The font size of all fonts within the application is correlated to the size of the system fonts used by macOS. We are not going to change that.

What about the avatar?

Scales with resolution in the same way as font size