Even though right now I don't have access to an M1 mac (had to return my development transition kit to Apple), I have a suspect - I think with the latest XCode the launcher gets compiled both for Intel and ARM but the rest of the binaries is Intel-only so the launcher is started as an ARM process but then loading the code from dylibs fails as they are Intel.
I tried to disable ARM code generation for the launcher and uploaded a new installer for you to test - would you give the following file a try?
https://download.geany.org/snapshots/geany-1.38_osx-2.dmg