The main thing is being able to handle transcoding for certain clients that need it. I’ve got it in Docker on an oldish workstation I bought for like $100 on eBay and threw an SSD in for the OS, but that thing’s surely serious overkill. If you’re only streaming to one or two clients at a time, being on a wired network and having hardware support for any codecs you’ll be dealing with are probably the most important factors.
Kodi on an Rpi makes a good cast target for it, though.