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 think your link is wrong (that’s the one that causes Archive.org to try a new capture). I got it working with this:
https://web.archive.org/web/20230613091704/https://old.reddit.com/r/help/comments/135tly1/helpdid_reddit_just_destroy_mobile_browser_access/jim40zg/
Someone else mentioned this and I fixed the link. I wonder if the edit isn’t spreading to other instances for some reason.
No one else is mentioning tthe post is over a month old.