So it's clear, for now only the following boxes do Forever, SLY UK, DE, IT and BT Sport...
Viark (closed & android) - Best in the business
Geant (android) - Not sure, others say they work ok
GT Media (android) - Again not sure what others think
Boxes that open sky need to have one of these chips:
Hisilicon 3798 MV 200
Hisilicon 3798 MV 100
Rockship RK3229
Ali-M2661
Ali-M2662
Ali-M 3526
Ali-M 3521
The first three chips are for android 4k boxes. The hisilicon ones are no longer produced. All the new boxes coming with android have the RK3229 chip.
The first two ali chips are for closed source linux 4k boxes eg: ali m2661: starsat 200 4k , starsat 220 4k.
Ali m2662: Gtmedia v8 uhd.
The difference between the 2661 and 2662 is only the extra C/T2 tuner on the m2662.
The last two chips are for low cost full hd h265 (not 4k) boxes. The difference between m3526 and m3521 is that the m3526 have an extra tuner dedicated to SDS: CS via satellite (doesn't need internet connection).
I suggest you buy a starsat 220 or 200 box it's more stable than android boxes and half their prices and has a fully capable s2x tuner.