Board Game Arena

Hive has slight first player advantage (a bit more than chess), so all official tournaments online (not on BGA) are played with double rounds (white and black against the same opponent). However, until you don't get to expert level this is barely noticeable. In particular, learning defensive techniques hugely improves the way you see at tempo and all. Check on discord and youtube channels, there are quite a few resources out there https://www.worldhivetournaments.com/online-komunity/