Yes! Fixing game breaking bugs, and uploading builds for more platforms (Windows, MacOSX, Linux, Android, iOS, any other port of LÖVE) is allowed and encouraged.
If you do change the game in some aspect, it’s better to leave the Jam entry as it is, and upload a post-jam build of the game with the changes applied.
And this is also encouraged, post-jam versions are great! You take in the feedback people left and make your game even better.
Have fun playing and rating