'Mozilla developers plan to remove support for using the Backspace key as a Back button inside Firefox. From a report:

The change is currently active in the Firefox Nightly version and is expected to go live in Firefox 86, scheduled to be released next month, in late February 2021. The removal of the Backspace key as a navigational element didn't come out of the blue. It was first proposed back in July 2014, in a bug report opened on Mozilla's bug tracker. At the time, Mozilla engineers argued that many users who press the Backspace key don't always mean to navigate to the previous page (the equivalent of pressing the Back button).'

-- source: https://news.slashdot.org/story/21/01/11/1551224

Cheers, Peter