I installed mali-g610-firmware on R5b via RebornOS software install tool (welcome screen/utilities) it applied gpu acceleration to chromium and other applications. I rebooted and it worked great.
In chromium - webglsamples.org aquarium - 1000 fish 60fps, 5000 fish 32 fps.
YouTube video playback 4k 30fps - zero dropped frames
In Firefox - webglsamples crashed everytime.
YouTube playback - same as chromium, with one small exception… dropped 37 frames in first 400 frames then zero in next 3000 frames.