For those among us who are menstruating: drip. is a very neat little period tracking app that offers basic tracking functions and fertility planning. All data is only stored locally.
It is open source and was developed in Germany. It’s available on Android and iOS.
More information in https://dripapp.org/
I don’t ovulate due to having too few X chromosomes, but that’s an awesome name for the app
there’s also a “how to condripute” section on their website.