Basically that. Everything seems to work as intended other than that running Jazz Jackrabbit 1 (option 1 in the dosbox menu) only shows the welcome screen and doesn't actually run the game. It did run a couple of times in the very beginning, but unreliably, and recently it hasn't at all. I've tried reinstalling, no use. Holiday Hare (option 3) runs as it should.

i'm having the same issue. windows 11. uninstalling gog galaxy and running the game from the "offline backup game installer" from my game library in the web version of gog worked once, but no dice since

Same problem here!

Workaround for now:
1. Create a new folder inside of the "Jazz Jackrabbit" game folder. I named mine "JAZZ1"
2. Copy all game files (basically all files in the main folder, excluding the other folders) to the new (JAZZ1) folder.
3. Edit the "dosbox_jazz_single.conf" file with notepad:
change the part

:jazz
cls
jazz.exe
goto exit

to

:jazz
cls
cd jazz1
jazz.exe
goto exit

(if you named the folder differently, insert the name instead of jazz1 after "CD")
4. Save the file and try to launch the game!