Is the liluo upload obligatory?
because I keep getting something called "request error 403" whenever I try to build it there, so I don't think I could upload it there
It's required as one of the conditions for winning, but you can add it after the deadline on itch has passed if you're having trouble getting it to upload.
Try to reduce the size of your game(Check near the end of the optimization video we have to see how to do that), make sure your internet connection isn't having any issues, and try the usual "turn it off and on again". 😅
If you're still having trouble, try reaching out with screenshots to the GDevelop communities on discord/reddit. 👍