In my game's folder I have 2 executables :
Lazers.exe <- My game's executable
UnityCrashHandler32.exe <- A thing Unity is making by default

The Itch.io app is launching UnityCrashHandler32.exe, what can I do to make it launch Lazers.exe ?

The latest version of the app is launching the right .exe, my bad !

For any future people that find this topic, you can control what executables your game uses in the app with a manifest file. You can learn more here: https://itch.io/docs/itch/integrating/manifest.html