Nvidia shield is usually regarded as the gold standard for Android TV devices.
The Shield is also one of the only Android TV devices that passes on HD audio codecs, so if you stream any Blu-ray rips with DTS-HD Master Audio or Dolby TrueHD and you want passthrough to work correctly, you probably want a Shield.
What’s your budget? The Walmart ones might be all you need. Do you really need it to be Android TV? I have both Roku and Google TV clients. I like the Roku one, but not a fan of the closed ecosystem (can’t side load or adb).
You shouldn’t need anything crazy to play your media, but if you go with Google/Android please replace the default launcher. You will very happy then lol.
I am looking for something that’s relatively cheap and minimal <50€
The Walmart “onn.” has been perfect in my household. Dirt cheap at $20, degooglable, good remote (you can use an app to rebind the streaming service buttons to apps you actually use). Supports the Google cast protocol and also SmartTubeNext. No ads of any kind on the home screen, because I’m using a custom FOSS launcher.
You can sideload Roku devices. Hit a button combo on the remote and it enables developer mode and a web page you can upload the package to. It’s been a long while since I’ve messed with it so I don’t remember many specifics
A TV box from AliExpress.
Don’t do this as it will come with malware preinstalled.