There is no "Universal" RK3229 Android 9.0 firmware. Flashing the wrong board variant will result in:
Technically, Rockchip never released an official Android 9.0 SDK for the RK3229. The community firmwares are franken-builds: using an RK3328 (similar architecture) Pie kernel patched to work with the RK3229’s DDR3 memory controller. Rk3229 Android 9.0 Firmware
Access to newer versions of streaming apps that no longer support older Android iterations. There is no "Universal" RK3229 Android 9
RK3229_9.0_MXQ_4K_SSV6051_20210603.img RK3229_9.0_AP6212_2GB_16GB_20201111.img RK3229_9.0_rtl8723ds_vontar_20210920.img RK3229_9.0_XR819_t95_20210115.7z Rk3229 Android 9.0 Firmware