As far as motherboards go, you would probably be fine with any consumer desktop brand but you should probably look for something with dual NIC. If you want something a bit more robust AsRock Rack has some really great options. I've been using the X470D4U for about 4 years now without any issues.
For your CPU I recommend Ryzen 5700G. Powerful enough for everything you want to do, the TDP is only 65 watts so it's not going to destroy your power bill, has a decent integrated GPU, and costs only about $200. Another positive is that it uses DDR 4 so you can load up on that for pretty cheap too.
I can second this. It took a while after an update for the domain to show properly and not give an error. I don't know exactly how long but I started it in the early morning and it wasn't working but by 11 am it was all sorted out.
The allowed IP's for your peer should be 0.0.0.0/0 NOT /32. (That literally means that only IP 0.0.0.0 is allowed). I'm pretty sure that's your problem since 0.0.0.0 is not a valid IP that anyone is assigned.
Plenty of multiplayer games need to run a server so you can play with your friends, not always cloud based. Would Verizon require a business class account to host a multiplayer session for Halo on your Xbox?
But seriously, I'm sick of these stupid headlines. Write an article when you know the details not when you are speculating on them. There is nothing new here.
I get that this is a big deal but why do the headlines need to fluff it up to make it seem like there is a human out there? When do we ever say that our rovers on Mars are going for a Mars walk or stepping off their landing platform? If it's wheels they are rolling or going for a drive! It's no wonder that trust in news media is declining when there are editors who think this kind of bullshit can fly in a science headline.
For your local PiHole DNS, where are your records for your domain pointing? I believe you should have an A record for *.example.com that points to the IP of your NPM server and then an MX which points to the IP of your mail server. If this is already the case then you can ignore this.
Also, if you are using DHCP do not have it assign your public domain to any of your hosts because that could screw up name resolution as well.
As far as motherboards go, you would probably be fine with any consumer desktop brand but you should probably look for something with dual NIC. If you want something a bit more robust AsRock Rack has some really great options. I've been using the X470D4U for about 4 years now without any issues.