Yes, you can use the controller for 100% of the game, I was reading some of the comments and they don't particularly explain why using menus suck, you practically have to use the joystick as a semi mouse with way to much sensitivity. I rock the same setup as you, only including a wifi router for Quest 2 PCVR, haven't touched a keyboard in months.

Many players loved the successful game Mount and Blade: Warband. Given the game’s success and awesome singleplayer, people have been bugging TaleWorlds to implement a co-op feature in the next game Mount and Blade II: Bannerlord so that they can play singleplayer with their friends. Unfortunately, even after waiting an eternity for the game

Fixed a bug that disabled siege menu buttons due to the player not being recognised as the siege leader. Fixed a menu text bug that occurred when a higher-ranking lord joined the player's siege event. Fixed a bug that caused the player’s siege to advance to the keep battle even if the player retreated in the mission.
Full Invasion 2 is a multiplayer modification for Mount & Blade: Warband. In Full Invasion 2 players cooperate as a team to survive against as many waves of invaders as possible in Invasion game mode. This multiplayer mode only module is an approved and supported sequel of Full Invasion mod by Arch3r.
Just no factions or npc lords. Bannerlord Coop - project that is closer to what you’re looking for, campaign map, all the same factions and npcs, 1-4 players on the same map playing together. Mod is still in early development tho and probably won’t see release for a couple years. Invasion - steam workshop mod where you play battles vs
If none of the workarounds did work for you, you can try to launch the game via the TaleWorlds.MountAndBlade.Launcher.Singleplayer.exe and TaleWorlds.MountAndBlade.Launcher.Multiplayer.exe files located in the folder:“:\SteamLibrary\steamapps\common\Mount & Blade II Bannerlord\bin\Win64_Shipping_Client”. (Please note that these files are
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is mount and blade 2 multiplayer