Hopefully Software Freedom Conservancy's GPL compliance lawsuit against Vizio will result in more of the necessary source code becoming publicly available, merged into existing operating systems like OpenWRT, Alpine or Debian and then projects like Kodi or KDE Plasma Bigscreen ported to run on top. If Conservancy win under their current strategy, then that would enable any recipient of a Linux based TV to sue the vendor for GPL compliance.
Seems acceptable from a warranty pov. Obviously if they refuse to replace your cracked screen because you've changed the firmware then it's unacceptable.
https://sfconservancy.org/copyleft-compliance/vizio.html https://plasma-bigscreen.org/