That probably counts as a privileged page, as in something uBlock Origin can’t access or modify.

Mozilla has probably been running another “experiment”, meaning not every user is affected. In the past they claimed it’s not advertisements because they are “continually looking for more ways to say thanks for using Firefox”. (Bullshit.) If you go to Settings > Home, you disable anything you don’t want to see, or just set your home page to a blank page, period.