There is this app called gadgetbridge.
I'm wondering if somebody is using it? What fitness tracker device are you using with it? Apparently not every supported deviced is supported in the same way as it says on the website: "(WARNING: Some of them WIP and some of them without maintainer)

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I have been using gadgetbridge for years and I am very happy. I currently have an amazfit gts2e, a zepp e and the sony wf xm4000's configured. I think there is no better option to use smatwaches without giving away your data to third parties.

I have been using it with my Pine Time and I havent had any big problems so far. I did have a issue where it would lose connection with the watch but that seems to be resolved by changing to the unrestricted battery usage setting in app info.

a year later