In my notebook I have dualboot with Windows 10 and Ubuntu 20.04, and in Ubuntu Firefox notifications are integrated with the system, but in Windows 10 the notification is a ugly white rectangle. I tried to search how to change, and one site said I have to go to to Settings>System>Notifications & Actions and scroll down to ''Receber notificações destes remetentes'' and turn on Firefox, but Firefox don't appear there, as you can see in the screenshot. I'm Brazilian, so my system is in Portuguese.