Garling

I have ANTIK Set Top Box and want to replace it's original OS/Firmware with any common linux/android (linux preferred), because the original OS is locked & proprietary, and i want to use OS that are more flexible. STB brand : Antik machine : b2067 cpu family : sh4 cpu variant : st40-300 cpu type : STxH205 Is there any OS/firmware that i can use? or any help/guide on how to do this is much appreciated, Thank you.