Several of the links at the Nextcloud app store page for Phonetrack are outdated and broken, referencing https://github.com/julien-nc/phonetrack-oc instead of https://github.com/julien-nc/phonetrack.
There’s already an open issue about that in the corresponding GitHub Repo: Link to Homepage wrong · Issue #27 · julien-nc/phonetrack · GitHub
I see. Apparently my cursory search of the issues was insufficient.