@alexkornitzer thank you for your dedication on this. My 5 cents:
I've been able to log in several weeks ago without any issues using an RC version. It obviously became problematic once I got logged out. However, I've noticed there was an issue with their GraphQL API even before I got logged out. Twitch has a functionality which allows you to sort of "announce" a resubscription to a streamer in the chat. It shows a popup allowing you to share a custom message. This worked, however submitting this form yielded a checksum error on the GraphQL API. This might be related to their new anti-bot protection, or maybe not, who knows.