The best solution at the moment is using an nvidia shield (2019) instead of a PC:

• it's tiny
• it's fanless
• it's got low power draw (5-10w)
• it can do 4k, hdr, and dolby vision (most importantly, it has the best support for these among services. good luck getting 4k video from netflix, disney+, and amazon on a PC)
• it has usb ports for dacs, controllers, external drives, and keyboard + mouse
• you can sideload android apps including ad-free home screens, remote button remappers, SmartTubeNext as a youtube replacement frontend, and moonlight for game streaming
• you'll have the most up-to-date and best supported versions of apps like jellyfin and plex
• it has pretty much the best selection of audio/video codecs, so you shouldn't need to transcode anything
• you can set up the nvidia shield remote to control tv power and volume on the tv or on a separate av receiver

To add to everyone else, I moved from Kodi to Jellyfin and it was a game changer for my home server solution. (I run the server off of my gaming PC)

Just use a Chromecast. You can use it from every device (phone/laptop/tablets) on the same WiFi.

My go to is Roku.

Cheap, always works, compatible with everything

You could try a Google stick?

I would recommend trying different skins for Kodi, was a game changer for me.

Pi with Kodi on it is pretty good.