Personally I replaced my TV Box with a Intel N100 Mini-PC (specifically a GMTek G3) running Lubuntu and Kodi, though it's used for a lot more than just being my TV box. I also got one of these remotes so I control it just like I would a dedicate TV Box (even though it has a mini-keyboard on the back and airmouse functionality, I almost never use it).

I use IPTV with it to watch just the free TV Channels, though there are providers out there who carry over 1000 channels for 5 bucks a month.

If you want something to just use as TV Box, start by checking Libreelec which is a Linux distro with Kodi configured to just work as a TV Box. It has builds for a whole lot of single board computers, which generally are cheaper than Mini-PCs (for example you can get a Banana Pi M5 - one of the supported SBCs - plus box, powersource and even the SD card for about half the price of the Mini-PC I got). The same remote I use should work fine with Libreelect on any platform which has at least one USB connector (not tested it myself but it makes sense since it uses the same kind of protocol and dongle as a wireless keyboard + mouse with pressing the "normal" remote buttons just generating keypresses according to some kind of standard of shortcut keys for media players)

Had I've been aiming for just a TV Box replacement I would've probably gone via checking which hardware Libreelec is compatible with and then chosen one of those and used the Libreelec since it's a Linux distro already preconfigures for acting as a proper TV Box (whilst with Lubuntu with Kodi on top I had to go around figuring out and changing the configuration for auto-login, auto-starting Kodi on startup and so on)