The GOG version is DRM-free and excellent for LAN parties. It comes pre-patched with the community fixes.
Before you launch, disable Windows Defender Firewall (just for the initial connection). You can re-enable it once the match starts. Alternatively, add the game as an exception. how to play stronghold legends multiplayer lan extra quality
Does that mean you cannot play? Absolutely not. The best way to experience with extra quality (meaning high resolution, no lag, and no crashes) is via a Virtual LAN (VPN) or direct TCP/IP connection. The GOG version is DRM-free and excellent for LAN parties
The Steam version automatically updates to the latest patch (1.4.1 as of recent updates). It includes native widescreen fixes. Right-click the game in your library > Properties > Betas. Ensure you are not on an old beta branch. how to play stronghold legends multiplayer lan extra quality