Unfortunately I don't have an iOS phone so testing/troubleshooting on a real device would be very difficult for me. Also it would signifcantly increase the effort to keep everything uptodate because I am the only contributor so far and Apple's developer account costs 100 EUR/year, which is a lot for an open source project.
Edit: I would have to charge for an iOS app because I don't want to spend time and actual money to offer an iOS version. At the current state though I cannot realistically say if there is even enough demand for it. Also, charging for it would turn this from a hobby project into a side business, which comes with different expectations and responsibilities
I am tracking my location now for nearly a decade to create some Google Timeline alternative. Therefore I used OwnTracks before but wanted to have more control over the tracking settings and how data is synced to my own backend (e.g. only every 15min and only with WiFi). It supports syncing the location data to a selfhosted backend but can also be used purely as offline GPS tracker and has some other features (like geozones) which improve battery efficiency
Edit: I would have to charge for an iOS app because I don't want to spend time and actual money to offer an iOS version. At the current state though I cannot realistically say if there is even enough demand for it. Also, charging for it would turn this from a hobby project into a side business, which comes with different expectations and responsibilities