If you want to do a HDMI run then check the specs for HDMI because there's a max length recommended before you might have signal issues. Remember HDMI is digital so it's not that you'll see image degredation at length, it'll just stop working if the run is too long. You can buy active (powered) HDMI boosters.
Other options are HDMI over Ethernet, Ethernet is rated up to about 100m so a good choice, plus Ethernet cables are typically much easier to hide as they're smaller than the bulky HDMI ones.
There's also a number of other wireless capable streaming devices if you don't mind a tiny amount of compression that most of these things come with, Steam link is one option but there's others on the market.
There's also wireless HDMI devices but In my experience they're quite expensive and for some reason quite bulky.
I personally just run HDMI but then my PC and home theater are both in my living room so that's a short run, but easy to hide, there's a number of products that will hide away cable runs around skirting board and alike.