We deal with a parallel challenge in the Android TV / Google TV space: modern updates (especially Android TV 14+) continuously tighten restrictions, killing accessibility services and forcing OEM bloatware launchers.
Achieving clean, durable control often comes down to clever non-destructive ADB flows (setting home-activity handlers, disabling stock packages per-user without bricking OTA updates) rather than fighting low-level boot chains. Always respect people pushing hardware beyond its artificial walled-garden limits.