There are downsides with downloading their app just to input bad data, but it's a fun thought.

edit: While we're at it we might as well offer an alternative app to people.

I posted in [email protected] to collect recommendations for better apps

The post: https://lemmy.ca/post/32877620

Leading Recommendation from the comments

The leading recommendation seems to be Drip (bloodyhealth.gitlab.io)

Summarizing what people shared:

• accessible: it is on F-droid, Google Play, & iOS App Store
• does not allow any third-party tracking
• the project got support from "PrototypeFund & Germany's Federal Ministry of Education and Research, the Superrr Lab and Mozilla"
• Listed features:
  • "Your data, your choice: Everything you enter stays on your device"
  • "Not another cute, pink app: drip is designed with gender inclusivity in mind."
  • "Your body is not a black box: drip is transparent in its calculations and encourages you to think for yourself."
  • "Track what you like: Just your period, or detect your fertility using the symptothermal method."

Their Mastodon: https://mastodon.social/@dripapp