Oh, I probably should have clarified that was what I was asking. Plenty of people run Windows on their PC's and Linux on their servers.
Mint is often recommended since it has a very similar experience to Windows. Ubuntu gets used quite commonly on servers and is a nice choice for getting started. If you are looking for a stepping-stone for a more advanced one then maybe Manjaro, a beginner friendly one based on ArchLinux (a minimal distro with a very hands on installation process, which has excellent doc and community). In any case you don't have to worry about locking yourself in with a distro pick. All of these use systemd for init system/service manager, and other than the package manager, pretty much everything else is interchangeable.
Wow, didn't know ISP's got THAT strict. Forget running a server at home, here you won't get in trouble for torrenting on a public tracker. Who would penalize them, the IANA?