This is a really weird issue that I've not entirely pinned down.
For Lethal Company I've been using Thunderstore Mod Manager to install and handle my mods.
After upgrading to the R3 I've noticed that the mod software has intermittent issues downloading mods, retrieving the full install list and sometimes doesn't connect at all.
Weirdly, this only really happens with one computer, the other desktop runs fine. It akso only happens with Lethal Company, other games via the same mod manager connect find.
This had me thinking it was a computer issue rather than network however the second I switched my computer to a different network (tethered my phone) it worked fine.
Even weirder, it then worked fine over ethernet again for a while before the issue cropped back up. Seems it happens when an update for a mod is detected, the whole thing just hangs. Switched to tethered network, updated mod, reconnected over R3 ethernet and it worked again.
Any firewall or network limitations via R3 are OOTB so I'm stumped. Attached are the IPs they say they use but I'm honestly a little stumped