Do any privacy respecting, powerful, health/chronic illness tracking apps exist?

I've used Bearable and Flaredown in the past. I'm able to (somewhat) use my Garmin sports watch with Gadgetbridge (but I only use it for heart rate and sleep). But now I'm needing to try and find patterns in my health again. Yeah, there's still Bearable but I don't like the way it's set out and I don't think it's open-source. Flaredown seems to be dying? There's no android app any more anyway (which isn't absolutely necessary anyway). I've seen suggestions for Guava but it gives me ick vibes (yet to read the privacy policy) and it has AI in it which I will not at all trust not to accidentally leak health information.

Something Obsidian md (PC) based would be fine but I don't know of any plugins that can algorithmically pick up and display patterns and correlations from data.

EDIT: For clarity, I don't mean things like Garmin's app for tracking steps, sleep, exercise, etc. I mean apps (phone or PC) that allow you to have a food diary, track pain levels, illness, sleep, water intake, stress, menstrual cycles, symptoms, etc. - more for tracking chronic health issues and finding correlations, patterns or behaviours that result in worse symptoms or symptom improvement. :)

Suggestions? Ideas for alternative methods to using apps?

Not that I'm aware of. Garmin actually has an excellent privacy policy, but that is of course, subject to change at any time. But that's probably the closest thing.

Wanderer (AP Strava alternative) just released a new app that looks great but not sure if that's the "health app" you're looking for.

https://wanderer.to/app

Does their tos allow them to share/use it while it's available (in aggregated form or otherwise)?

These are all android apps I get from fdroid:

I use drip for menstrual cycles (wish it had more options)
https://f-droid.org/packages/com.drip

Pain diary pfa for a pain diary (wish it had more zones/areas)
https://f-droid.org/packages/org.secuso.privacyfriendlypaindiary

Waistline for calorie counting/food diary, weight tracking (wish adding food was not manual)
https://f-droid.org/packages/com.waist.line

Medilog can do a lot of tracking like fluid intake, weight, glucose, blood pressure, temperature, oximeter, and simple mood.
https://apt.izzysoft.de/packages/com.zell_mbc.medilog

Gagdetbridge kinda tracks sleep but I get what you mean, I wish I could rate my sleep

There's more apps on fdroid if you search for "health" that I haven't tried yet like harp seems interesting so I just downloaded it
https://f-droid.org/packages/xyz.lepisma.harp

This is my first time looking at Polar, but they have a giant thing in bold at the top of the privacy policy:

Your personal data is never sold or disclosed to third parties without your explicit consent, unless required by law.

https://www.polar.com/us-en/legal/privacy

I'm not really knowledgeable enough to ever feel confident about analysing whether apps are truly privacy respecting. So, I'd suggest look into these for yourself and see what you think.

I'm using Mooneva for a period tracker that helps analyse signs and symptoms at different points in your cycle.
https://f-droid.org/packages/com.mooneva.app

Someone else mentioned MediLog. It can be used for lots of stuff. I'm just using it to monitor my weight because I don't need the other pieces at this point.
https://f-droid.org/packages/com.zell_mbc.medilog.fdroid

And when my body is being weird and I want to look for correlation with my symptoms and my diet, I use Life Notes.
https://play.google.com/store/apps/details?id=com.sebferrer.life_notes

Mooneva is 100 times better then drip. I used drip for years and when changed and I am very much satisfied.