libreddit is suffering the same problem. Some instances are still working but they're probably switching outgoing IPs often to evade the ban hammer.

As others have noted, I think this is part of a larger trend. All websites have realized that data is power, data is money, and they don't want to share anymore.

I used to host both nitter and libreddit, now I host neither of them. I've simply given up on reading that data.