Davx⁵ has Mac OS caldav carddav server integration so you can sync with it.
https://www.davx5.com/tested-with/calendar-and-contacts-server
On android you can use simple calendar or etar to view calendars and "tasks" or jtxboard for tasks/journals
Radical, Baikal, or NextCloud.
Then sync with your phone via Davx5
If you're willing to self host Nextcloud then that could be a solution.
Currently I use it to sync my calendar on my phone and an instance of MagicMirror2.
You don't necessarily need to self-host Nextcloud for yourself, you can pay a provider to do it for you, of course, at a price, or free but with limitations, like The Good Cloud.
You can also try EteSync.
And in F-Droid there are many apps to integrate your Nextcloud instance with your device, my favorite are Ente (for calendar), Tasks(dot)org and Joplin
Nextcloud should be good for that. There are a bunch of services which offer a few GB for free, which should be enough for your needs.
I agree that Nextcloud is a great solution. Some other cardDAV and calDAV solutions exist, but Nextcloud provides much more. Here is a little demo of Nextcloud on a handset. https://videos.trom.tf/videos/watch/5fc16e0e-f95f-45a2-9843-37749bf9dada
Get etesync
etesync looks amazing, it is a shame that it looks a little bit complicated to set up
Its not complicated at all. For one its a paid service so if you can afford it do it. If you wanna do it free you have to host it yourself
I tried almost every possible solution suggested here, but i couldnt manage to make it work, I'd really like a simple guide on how to set something like this or a self-hosting solution, though i dont even know if i can do that without a server
I have been using simple calendar.
Try Proton Calendar
F-Droid is an installable catalogue of FOSS (Free and Open Source Software) applications for the Android platform. The client makes it easy to browse, install, and keep track of updates on your device.
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