So Im assuming you refer to Bannerlord Online (BO) that is a fan-made multiplayer (MP) mod. Currently at this point, in terms of stability, administration and code, Id say its one of and prolly the best MP mod for Bannerlord. Its basically singleplayer campaign but in MP. Granted, some singleplayer features is missing due to the obvious implications they have in a MP environment, but the concept is there and development is on-going, new features and mechanics is added at a somewhat frequent basis.
I suggest you go to their forum and poke around, find a clan you like and join them. VOIP is almost essential for clan business. You can also play solo, many players in BO play solo, they trade, PvE and some of them tend to poke around in the PvP zone and troll the clans.
Good luck and enjoy!