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.
I deleted my 10 year and 5 year old accounts. I didn’t purge my posts and comments, as I doubt they’re truly deleted from the database and I wanted to leave that content for people who aren’t reddit. I’ve moved to the fediverse, andi think I’m here to stay.