Two Game copies on two different Steam accounts, Two Computers, Same Router - Game kicks us out of the Server

[Tuletar 0]

What are the latest workarounds to solve this type of problems?

I've tried opening TCP/UDP Port 27024 on my router and adding 

+clientport 27024

or
-port=27024

on one of Steam account's/PC's but the problem persists.

Also, I checked via netstat -aon in cmd.exe and game doesn't seem to go through that port whatever I try.

Do these these launch options still work or can I resolve this in some other way in 2023?

Could it be solved from the server side, it's a community server, maybe I could ask the owner, but I don't know which settings should they change?

Thanks everyone for any help in advance.