After many weeks of research, testing and debugging I managed to put together an Unofficial Armbian Linux build for LinknLink iSG Box SE.
Version: v26.05 Rolling
Kernel: 6.1.115-vendor-rk35xx
Flashed and booting from eMMC.
All hardware working and tested, including Ethernet, WiFi and Bluetooth.
Source, build and flashing instructions here https://github.com/luisdosreis/linknlink-isg-box-se-armbian
If anyone is interested I can share a test image ready to be flashed or you can (and should) build it yourselves.
I plan to add a Home Assistant flavor to the build system in the future.