We will add additional logs to the launcher in the future to see whats going on in these cases. Until that time 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 below:
“...:\SteamLibrary\steamapps\common\Mount & Blade II Bannerlord\bin\Win64_Shipping_Client”
I've been checking around and found that this issue happens for other games as well. Has something to do with how the game is communicating with Steam or something.