Yesterday (19/08/2023) everything worked fine. Today (20/08/2023) I can no longer login to Twitch using Firefox. I restarted browser and cleared cache. No change.
EDIT: I tried again after 30min and it works again. I have some privacy-oriented plugins but I don’t play with custom useragent.
Oh I fully understand a smaller company having a website that says “some animations may not work with your browser” when it’s obviously easier to just do chromium as that covers almost every browser, but fully disabling the entire website when it works just fine as long as you tell Firefox to say it’s chrome is a different story.