I actually did a bit of a shortcut on ARM, since some of those chips are as bad as Intel's or worse. For example, the rPi was criticized for a long time because

I actually did a bit of a shortcut on ARM, since some of those chips are as bad as Intel's or worse. For example, the rPi was criticized for a long time because the CPU was essentially subordinate to the GPU, whose code was binary-only. That seems to change now. The issue with recommending suitable ARM chips is that there are so many different ones by all kinds of vendors following all kinds of philosophies. In fact it's the first time I heard of that particular chipset vendor. I looked at the chip's specs: Like most current ARM CPUs it comes with TrustZone (including advertising for a "trusted video path"), so an important part to decide if that's an open system is to check what code is running in that mode, and if that can be disabled or replaced. The open sourced u-boot code might be able to give insights here. The other thing is Mali graphics: those come with a closed source graphics driver. There's a reverse engineering project (lima), but they're relatively small and thus easily outperformed by chip vendors (release new iterations of the hardware every 6 months, and they'll never be able to support everything). Sorry that I can't give detailed answers, but it's just too much to stay current with the entire ARM market.