1. Open the Steam library
2. Find Cossacks II: Battle for Europe, then go to properties
3. Go to the compatibility tab and select the version Proton 3.16-9
4. (Only for SteamOS) Open Desktop Mode

The game does not start in Gaming Mode

1. Open the game properties again
2. Uncheck the Steam overlay checkbox
3. Launch the game
4. Go to game settings
5. Change the resolution to 1024×768

Higher resolutions cause very frequent crashes after winning a battle, so that progress is not saved and you have to repeat the same battles many times

1. Select a game in the Steam library
2. Click on the controller icon
3. Select the selection of community controller schemes
4. Use the scheme named “Steam Controller / Steam Deck (very comfortable)”

In the scheme I have included all the buttons and shortcuts used in the game. It was created for Steam Controller, but it work comfortably for Steam Deck as well