You can find technical discussions and file mirrors on repair communities like KenotronTV or through manufacturer help desks like Kogan Support , which provides specific instructions for similar Realtek boards.
Restores Smart TV functionality; specifically tuned for 4K UHD panels; fixes software-related power issues. Download RT2861P839 3840x2160 MAGIC 55&58 part01 rar
Once installed, users report the 4K output is stable, maintaining the correct aspect ratio for 55" and 58" screens without the distortion common when using generic firmware. You can find technical discussions and file mirrors