Getting Legacy Mode to work on a slow internet connection (where it takes more than 2 minutes to do its thing) is on the to-do list. It just doesn't come up very often that legacy mode is even required (but it is there for this eventuality), and combined with a slow internet.
If it takes longer than two minutes, the "Updating" screen will never disappear, but it still does the thing in the background. Give it say 10 minutes, then just reload the page and you're in business