One of the interesting ways in which this shows up is that in addition to email, RSS and calendars, Vivaldi has also actively promoted support for #Mastodon, in a very simple yet effective way (providing a Web Panel for their instance; you can add your own). I expect the same will work on other #Fediverse platforms, as long as they provide a functional web interface with good “small screen” support (since this is effectively what the Web Panels use).