Isn’t it easier to take ready-made firmware from another single-board device, for example based on ubuntu or debian, and adapt it for the TV Box?
Here I found a list of devices on sale based on RK3576:
Mini-PC
ROC-RK3576-PC - https://en.t-firefly.com/product/industry/rocrk3576pc
$159.00 USD - $189.00 USD
Android14.0, Debian12, Ubuntu22.04
EC-R3576PC FD - https://en.t-firefly.com/product/industry/ecr3576pcfd
$179.00 USD - $209.00 USD
Android14.0, Debian12, Ubuntu22.04
with case
Mekotronics R57 - https://www.mekotronics.com/h-pd-86.html
$140.00
with case
Debian, Armbian, Android 14, Buildroot
armsom Sige5 - https://www.armsom.org/sige5
$124.00
Debian, Armbian, Ubuntu, Android
https://docs.armsom.org/armsom-sige5
Banana Pi BPI-M5 Pro - https://docs.banana-pi.org/en/BPI-M5/BananaPi_BPI-M5_Pro
Armbian, Debian, Ubuntu, Android14, Buildroot
Boardcon EM3576 - https://www.armdesigner.com/EM3576_SBC/
Board + CM3576 SoM for DVR, 12 AHD inputs
Android 14
SOM
Banana Pi BPI-CM5 Pro - https://docs.banana-pi.org/en/BPI-CM5_Pro/BananaPi_BPI-CM5_Pro
Armbian, Debian, Ubuntu, Android14, Buildroot
Geniatech SOM-3576 - https://www.geniatech.com/product/som-3576/
Android 14, Debian 12
Forlinx FET3576-C System on Module - https://www.forlinx.net/product/rk3576-c-system-on-module-156.html
Linux6.1.57, Android
Forlinx FET3576J-C - ???
Boardcon CM3576 - https://www.armdesigner.com/CM3576_SOM/
Android 14
TV box
H96 MAX M9 RK3576 TV Box - https://www.h96tvbox.com/product/h96-max-rk3576-android-14-tv-box/