Same as typical UE4 game minus GPU requirement, you don’t need GPU for it at all actually, minus CPU time for rendering so CPU usage should liter, memory usage should liter too a little bit. Dedicated server still need to run game state, so it still require some CPU power and memory more then typical server software. You could run dedicated server your see and see how much it takes.
If you really need specific specs i think good way is to check is look on hosting services and see what specs do they use for hosting servers of UE4 games
I successed with cent os 8.3 even with apache , node.js process and mongodb . Works but bad delta time intervals (lags). I will comment my expirience with new clear 5$ centos min linux without any other installatin and running other threads… I run on http://IPADDRESS:8889 with html5 ue net driver …
Configuration: 1cpu shared 1gb ram .