Updated to Catalina – note to self 'do not update Apple software until it is at least x.1 version' – my normal browser is Firefox, but if I attempt to use Chrome, Safari or Opera, often they aren't able to connect to the Internet, in fact I can access none of the browser funcationality e.g. preferences. The only way is to reboot – a reboot or shutdown is often only possible by depressing and holding the power button.
An additional 'Feature' of opening a Mail link is that it opens two instances of Firefox.
Any thoughts on how this might be fixed are welcome, but I suspect I will have to endure until Apple provide a fix (speedily I hope!!).