Not sure how to actually submit a version of the game, but the ~6.5 GB I had to download was a bit much...
I just converted all webp images from the "Scenes" folder to avif images with a compression of 75%.
This results in around 2.5 GB less data to download.
The quality was also almost the same (checked on a 4k display).
Because Renpy does searches all images in the sub folders everything should still get found.
(I skipped through a bit, but didn't check everything)
I don't have a script on hand to change the videos and compress them appropriately, so the videos itself are still ~1GB.
So there's still quiet a lot of room for improvements.
Maybe I'll get to that at some point...
Here's the link, if anyone want's to download a bit less for almost the same quality:
Pixeldrain