I have set up a master password on firefox and the browser asks for it at unexpected time. Not every time in the start (so it isn't useful to "lock" the browser. Someone may auto-login to a website without typing the master password), just at "random" time.
How to Set Password in Firefox - YouTube Mar 23, 2013 How To Set A Master Password In Mozilla Firefox ! - YouTube Jun 12, 2020
Nov 27, 2019
How to Set a Master Password in Mozilla Firefox Mar 08, 2015 How to set up a master password | Firefox for Android Help Set up a master password so that you can use one password to access all your apps. To set up a master password: Open the Firefox for Android app. Tap the menu button (either below the screen on some devices or in the upper right of the browser) . Tap Settings (you may need to tap More first) .
Mozilla Firefox – Change Master Password - CodeSteps
Firefox fixes “master password” security bypass bug Aug 15, 2019 How To Protect Mozilla Firefox Browser With Password