Hey I found an open source menstrual cycle tracking app called Drip that doesn't call home to anyone and encrypts your data on your device. It's gender inclusive and it has a prebuilt version Android that you can get either on F-Droid or on their site here: https://bloodyhealth.gitlab.io
They have an iOS version but it's not pre compiled. I'll be working on that today so you can get loaded onto your Apple devices, along with the instructions to install it on said Apple device.
Please boost so others can see this!