I recently switched to Evolution on Gnome, and put all my notes, tasks, calendars and address books in a "radicale"[0] CalDav/CardDav server.

It's not 'slick' by 2021 app standards but it does what it needs to do pretty well. And compared to some apps, it uses almost no memory.

On my phone, I combine it with FairEmail, DAVx5 and OpenTasks.

[0] https://radicale.org/

I love the one that comes with elementary OS[0]. Looking at those screenshots, it seems to be a fork of Gnome's calendar?

I've connected it to both Google Calendar and Nextcloud's calendar, and it works perfectly well, provides notifications, recurring events, and I can quickly access today's events just by clicking on the clock on the bar. No complaints what so ever.

elementary's tasks app, on the other hand, is still WIP.

[0] https://github.com/elementary/calendar

Thank you so much, this is exactly what I've been looking for!

I've been using KOrganizer[1] for longer than I can remember. For better and/or worse, it's pretty tightly integrated with the Plasma desktop. For now at least, I use it with Google Calendar as its backend. Every once in a long while, it gives me some scary-sounding error message about failing to sync — but so far as I can tell the sync works just fine, albeit sometimes with a bit of lag.

I recently also started using it with my work-mandated Office 365 calendar. According to some docs somewhere that I can't find right now, there were quite a few hoops to jump through to make that read/write so I settled for read-only.

[1] https://apps.kde.org/korganizer/

Have a look at davmail. It's essentially a exchange to IMAP/calDAV... translator. I used it before with our work exchange server. It worked flawlessly (better than the imap support in exchange IMO)

So far I've always used Evolution and I like it pretty much. It even connects to my team's O365 stuff.

I’ve been using Morgen Calendar for a while. Although it isn’t open source, it works well on Linux, MacOS and Windows.

You could give Vivaldi a try

Holy shit, I hadn't heard of Vivaldi (nor its calendar) before!

I don't think I will leave Firefox for it but I might just use it just for the calendar.