Which health apps do you recommend?

I maintain my own list of open source software, but one of the biggest struggles has been finding open source health apps to add to the list. It seems like the open source community is lacking in this area, compared to proprietary counterparts.

I'm beginning to flesh out some of the health apps on my list, and I am looking for recommendations on which apps are generally used. This is an extremely rare circumstance in which I am asking for community feedback to add software to the list.

My preferred criteria is as follows:

Available for Android

It can be available for other platforms, but I tend to prioritize open source operating systems such as Android or Linux. In this case, a health app for Linux would rarely be useful. If available, please note whether or not the app works well with strict permissions on GrapheneOS.

Has a clear, distinct purpose

I prefer not to categorize the same app in multiple places. I am a believer of software being the best at one thing, rather than trying to be the best at everything. So, I would like to categorize different apps for each purpose (calorie tracking, nutritional information, fitness tracking, etc.)

Works entirely offline

Ideally, apps should work without ever requiring an internet connection. Having the ability to download data for offline use later is fine, if the data is large enough to warrant not being packaged with the app itself.

Still actively maintained

It's rare that I add outdated or abandoned apps to my list, but there will always be exceptions. The apps should be actively maintained, and have modern usability and appearance.

Those are best case-scenario criteria, your recommended app may not follow that. All apps should, of course, be open source. I am leaving the definition of "health apps" without elaboration on purpose, because I am looking for all health-related and physical wellbeing apps.

Thank you for your suggestions! :)