As quoted from the linked post.
It looks like you’re part of one of our experiments. The logged-in mobile web experience is currently unavailable for a portion of users. To access the site you can log on via desktop, the mobile apps, or wait for the experiment to conclude.
This is separate from the API issue. This will actually BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
The dev posted on r/Infinty_For_Reddit that he’s gonna try a subscription model first, and that he personally doesn’t use Lemmy, so there’s no Infinity for Lemmy client in the works, although he says that making Infinity For Lemmy should be easy with the API Proxy that the Lemmy Developers are making
link to the full post