Last month KDE announced a UI geared for big screens like TV’s, Plasma Bigscreen. Given this effort has the KDE organization behind it, I think it’s likely to be here for the long haul and have a healthy amount of resources behind it. I would like to suggest that Linux native client app be developed that takes advantage of Plasma Bigscreen.
Since Linux apps aren’t confined to constraints set by Roku and Kodi add-ons, it will probably be easier to develop and sustain, maybe even get better performance if someone writes it in something like Rust. Not saying logic end has to be written in Rust, just citing potential boons… program as you see fit if it seems worthwhile.