User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0
Steps to reproduce:
To reproduce (tested with the NVDA screen reader, but should be the same for sightet/mouse users):
Open the main Preferences dialog (Tools/Options)
Place focus on the list of preference categories (General, Search, etc)
If you're an NVDA user, enable Focus Mode; otherwise, skip this step
As a test, press the letter "P"; at this point, Firefox should ideally place focus on the "Privacy & Security" category; however, nothing happens and focus remains where it previously was
Focus stayed on the previously focused category.
Ideally, depending on the letter pressed Firefox should jump to the first category that has the starting letter of the key that was just pressed.