2 months ago - AndrewT - Direct link
When using Steam MP, all traffic goes via the Steam servers - being on the same network doesn't change anything.

But from what you say this seems like an issue on that 5GHz wifi network rather than a game or Steam problem. Have you rebooted or reset that router?  
2 months ago - AndrewT - Direct link
You tried HOI4 in both Steam and Nakama modes I guess?

But either way, I have no real explanation for what you are seeing there.