For Plex or jelifin. Either way you can install ready made distro like Truenas, unraided, Hexos(it has an easier interface for Truenas but got no idea how usable it is) or use a Linux distro like Debian and install docker then jelifin/plex. There are a lot of guides if you just search.

Hey, if you changed the Internet cable then the ip address most likely changed as well. Find you PC new ipv4 address and you’ll be able to connect

.1kWh is 100Wh

OpenWRT router seems nice but personally I need more ports

Ah just let a few of them die, how are they gonna learn

I’m not familiar with wireguard but I use Tailscale and it works really well

In my experience it’s not safe to port forward if you don’t know how everything works. Why don’t you use Tailscale? It works well and it even has Mulvad plugin