Prior to installing Catalina all pages would automatically open in full screen view, including my home page on start up. Since installing Catalina this no longer happens. Every time I open Firefox, I now have to go to the menu and manually select full screen view. Once I do this, all new pages then open in full screen view for the remainder of that session, but once I finish each session and close down Firefox, the same thing occurs next time I open it and commence a new session. In other words, there no longer seems to be a setting in Preferences to make this change permanent and avoid the need to have to manually select full screen view at the beginning of every new session.