Is it fully supported? Amlogic S905Y4

You’re asking about a device that hasn’t yet been tested with CE. Nothing is known for certain. Yes the s905y4 is supported, but there could be other hardware compatibility issues that have to be fixed.

Some OTT providers implement security features that only allow Android to boot. You will have to test and see if Android+CE can both boot. My guess is that CE will probably boot and work ok.

The s905y4 is a budget SOC (4xA53 CPU cores) on the weaker end. It will be ok in CE because CE has low hardware requirements. It won’t be very smooth in Android. USB2 is adequate.

Amlogic SOC classes:
s905y4 - low performance
s905x4 - mid performance
s922x, s928x, A311D2 - high performance

This other thread has a little bit of information about another SE box that is very similar to the one you are looking at.