It appears API rate limiting has effectively killed these alternatives. You essentially get nothing but “Too many requests” 429 errors.
Lemmy sadly does not have the active niche news and discussions I want. But now nothing can be read without going to Reddit. I hate Spez
Libreddit does work, but not all instances of it do.
A few I’ve found. But your subscriptions don’t carry between instances, and it’s hard try and cycle through them on mobile. And even then after a few minutes they start failing.