Used the MO2 installation script with a custom game config. Installed dotnet using Proton 4.11 up to and including .Net 4.5, then changed Proton to 6.3 to install .Net 4.6 through 4.72. Then changed back to GE8-23. Installed BLSE (https://github.com/BUTR/Bannerlord.BLSE) manually into the game folder and Harmony, ButterLib, UIExtender and MCM through MO2. This leaves you with a fixed base install. You launch the game which opens MO2 where you can start BLSE to run the game.