I may be unavailable during the time of the jam (not confirmed yet) and I was curious, how late is too late? I just want to know, just in case.

No worries at all! Late submissions can be managed by contacting me through Discord, Twitter, whatevers, and I cane send you a link to upload :>

The voting period ends 1 week after the game-making period finishes, so that will be a hard deadline. Thanks for the question, hope all goes well! ^^