Firmware for Rockchip devices is typically in an .img format. You need to find a firmware specifically built for " RK3229 V3.1 Search for forums like Armbian
You should see somewhere on the board:
(Thesis, 2023): This is an excellent deep dive into the firmware structure and forensic analysis of common Android TV boxes. It covers external network traffic capture, service identification, and vulnerability exploitation. Mxq Rk3229 Emcp V3.1 Firmware