I believe you could buy a random Android streaming box with an unlocked bootloader, and then install LineageOS on it. Not sure about the “streams from all the major services” part re: LineageOS, but last I heard it’s improving.

(There are also some boxes made specifically for this, usually sold as development platforms for STB products, marketed based on what SoC they contain. Though they’ll tend to be $200, while the random “finished product” streaming box will be more like $30. Both come with decent remotes.)

LineageOS on a cheap box will be L3 widevine, and fail play integrity, which means netflix and a bunch of other streaming apps won't even install. Even if you can get them to install, the L3 will stop you from viewing Prime, Disney+ or other similar services at anything better than SD.

I'm also interested in alternatives, but LineageOS on a cheap box isn't really one.