I just use an Nvidia Shield Pro. Runs all the streaming stuff, plus Jellyfin client. Use Jellyfin server on the PC.

You can still stream games and the desktop to it (sunshine on pc and moonlight on the shield), but they'll need mouse keyboard controller etc to be useful.

You could try finding a steam controller with the big touchpad circles. Using the keyboard with it isn't great but doable

Get an air mouse remote. Theyre like 20 bucks on amazon and you just point the remote at the screen to control the mouse cursor. Mine also has media controls on one side and a full keyboard on the other, and only one set of buttons works at a tim3 based on which side is pointing up so you dont have accidental button presses. It makes it way more functional if you want to do even casual web browsing and the media controls are great for htpc apps. You can also use in browser streaming services this way too though. Honestly one of my favourite peripheral devices that ive ever bought, and super cheap and works way better than i wouldve thought for the price.

Gamepad support for kodi is pretty sweet, if you got any of those to spare.

I use Kodi, and then install Kore as the remote.

Plus Xmouse as a second remote.

This enables HTPC usage from a phone.

https://f-droid.org/packages/org.xbmc.kore/

https://f-droid.org/en/packages/com.stripe1.xmouse/

Mythtv, Kodi... there are GUI's designed for this task.

I am using Kodi on an Androidtv box as a frontend, and a bluetooth mini keyboard/remote. Most times it is just start/stop/pause/ffwd, and sometimes text input - every two weeks or so.

If you can get a UI set up, like Kodi or something, I liked using my Flirc receiver on my htpc. You can use any IR remote, and completely map the buttons to functions. It was sweet.

Yes, the keyboard wont require regular use but you should still have one. You can use a frontend like I do, but there will always be little quirks or issues with updates so youll have to keep a mouse and keyboard handy, but you dont need to have it always visible or to use for the system, just for correcting problems.

I set up an HTPC for emulation and gaming. LaunchBox is my frontend of choice. Set up the PC to autoreboot every day at 3am. It only occasionally has an issue where LaunchBox crashes and needs to be manually restarted or something needs an update.

I use one of those $20 keypad controller things. Works really nice. Its wireless. You can tuck it away somewhere and you get full keyboard and mouse functions on a small controller.

I'd just run a web server on it and operate it from a phone.