Not sure if anyone else is experiencing this as well, but I have another bug that's hitting on my iPhone Xs/iOS 14.4.1/Safari.
I click 'Menu', and then 'Settings'. Then when I click the little submenu that defaults to 'Your account' to go to a different section, the screen dims but the sidebar doesn't appear. Interestingly, if I rotate my phone, the sidebar then appears, and if I rotate it back it's still there. If I start in Landscape, it doesn't work though. So basically to access different sections of Settings I have to start Portrait, click the submenu, then rotate my phone to Landscape.
I can post a screen capture video if this doesn't make sense.