Does upstream LibreELEC boot and work on “RADXA Starter Kit Rock ROCK 4C+ Board (Cortex)”? I prefer not download software from mega.nz (security question)
I’d start with trawling the Radxa forums and refererring to upstream kernel submissions. RK3399 is pretty mature at this point so as long as the device-tree files are in the kernel (or submitted so can patches can be picked to a self-built image) .. things probably work. That’s a rather vague answer but Radxa have been breeding/iterating boards a lot in recent times and it reached the point where tracking all the variants and sub-variants results in
For me still unclear if upstream LibreELEC works on the linked device.