I think is like firefly roc-3566-pc .
@mmie4jbcu tells he can boot with x88 pro 20, wich is similar, with box-demo but his dts is just a precompiled from kernel and this makes me hesitate.
You can test with his dtb.
I would use a roc-3566-pc image because the rock3a maybe patched because this sbc is a bit tricky.