What Calendar and To Do solution do you recommend?

https://programming.dev/post/13786766

What Calendar and To Do solution do you recommend? - programming.dev

I would like to have a central Calendar that I could sync everything to it, from my email calendars and my to do list, is there something like that selfhosted or not, that is FOSS?

On a related note, is it possible to sync all my tasks on Simply (fossify) Calender with a Caldev server. Also does anyone know if there is a good client with Caldev sync on Windows ? I know thunderbird has that functionality, but I would prefer a standalone calender instead of an email client.
I believe you can do this with DAVx5. I have calendars syncing to fossify with it.
GitHub - bitfireAT/davx5-ose: DAVx⁵ is an open-source CalDAV/CardDAV suite and sync app for Android. You can also access your online files (WebDAV) with it.

DAVx⁵ is an open-source CalDAV/CardDAV suite and sync app for Android. You can also access your online files (WebDAV) with it. - bitfireAT/davx5-ose

GitHub
Thanks for confirming
I have Simple Calendar synced to Nexctclouds CalDav using DAVx5, syncs just fine.