Soooooooooo I might have just ghetto fixed the bat file to work again.
I noticed I could download some attached files on posts from the site, but they were always failing in the downloader. I compared the links I got working on the site to the URLs in the cmd line that were failing and the URLs that worked were directing to https://data.kemono.party/*
instead of just https://kemono.party/*
. Not expecting anything to work, I messed around in the yiff.bat file in notepad and made a few tweaks under "def kp_patreon_assets(threadn, FAVORITE, CREATOR_ID):" Changing the "file" and "attachment" urls to include "data." in the url allows the downloader to now work again! I left the "content" URLs alone since I assume those are the inline assets like portraits we are able to download already.
You will have to manually edit this for fanbox / fantia / w/e as well. I got fanbox working as well, but I'm too tired to fiddle with it anymore. You will still need to hit X to force retry for some larger files or they just end up as incomplete .part files.
Hopefully that made enough sense for you all to also get it working again. Iunno, I'm tired as fuck and screwing with a batch file I've spent 5 minutes messing around in. Hope this at least makes some sense to someone.