could sombody write what Multiplayer sulution/Framework is best in 2021 in Unity

1. For game MainClient which is host, and 3-6 clients
2. For game where All players are clients conecting to a HOST

 

Maybe you should ask a different question, because I don't think it is possible to answer these ones.

Likely no one has personally tried every available networking implementation for Unity. Also, no one knows what "best" means in the context of your project. Best might mean easiest to implement. Best might mean the most features or flexibility. Best might mean whatever works and is the cheapest (aka Free).