I'm using Nextcloud for calendar and tasks, and I keep notes in plain markdown files that are also synced with Nextcloud. On Android I use Nextcloud Notes, Nextcloud Tasks and https://github.com/Etar-Group/Etar-Calendar
These are by far the best note and calendar apps I've used. Far better than Google's options. Apple's reminders are a bit better than Nextcloud Tasks, but the only feature I'm sorely lacking there is repeating tasks. Google doesn't support this either, which leads me to believe that it's a shortcoming of the CalDav spec for tasks.
If you're on Android, I suggest tasks.org, it supports repeating tasks even if the server doesn't. Of course that means you have to use it when completing a repeating task.
These are by far the best note and calendar apps I've used. Far better than Google's options. Apple's reminders are a bit better than Nextcloud Tasks, but the only feature I'm sorely lacking there is repeating tasks. Google doesn't support this either, which leads me to believe that it's a shortcoming of the CalDav spec for tasks.