OK, after some tuning I can confirm below setup is working fine for me with stable 30.4MH/s since 24H:

- clean and fresh Windows 10x64 Home installation + all updates
- latest AMD beta drivers
- AB 4.4.0 beta 16 with applied "voltage control" fix and this one
- no atikmdag-patcher applied
- 4x Sapphire Nitro+ RX580 8GB (11265-01-20G, HYNIX memory) with modded BIOS
- latest Claymore 9.8 with no overclocking/undervolting in BAT file

AB config: Screen shot
mv: 970
Power limit: +0
GPU core: 1250
GPU mem: 2150
Fan: 50%
Power from wall: 787W