Just dropping a post here for anyone wondering since it's a blizzard game. Multiboxing Diablo games is still allowed and i'm using isboxer for s26, same as the previous seasons, works great.

Hope nothing changes for Diablo 4, but seeing how Multiboxing botters overran Lost Ark, it's could be a problem similar to WoW and blizzard officially banning multiboxing across all their games.