ATnT should be able to tell you for sure. I remember reading about another person facing a cgnat using ATnT on reddit while i still went there so it very well could be.

And fairly easy setup yea. I did mine using a windows pc for testing as i was kinda in between places at the time and thats what i ended up using for jellyfin as well. Just lives on my media pc at the moment. The docs are pretty straight forward.

I recommend that or zero tier which is even more dead simple. Both are good but cloudflare does care about how much bandwidth you’re using so just bear that in mind if you think you’ll use the server for anything else.

Both are vpn tunnels so either should work just fine.

developers.cloudflare.com/…/connect-networks/

www.zerotier.com/pricing/

Self hosting can get pretty overwhelming but i find that using docs in addition to youtube videos helps a lot. I also recommend giving Linux a go when you feel up to it. It can be a very nice option if you’re working with older hardware.