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?