I use Xiaomi Mi Box S, as it works with official apps and additionally has Chromecast certificate.
But in places where Chromecast is not needed I use S96 Mini but flashed with https://www.atvxperience.com as it’s sometimes 2x cheaper.
Both are cheap but with price come lack of performance compared to Nvidia shield and such.
But didn’t test it with SmartTubeNext, as I’m using it mostly for IPTV/Jellyfin.
Thinking how will they do that? Is private browsing sending some additional headers?