This tempted me to try it. But I couldn’t get it to work in my homelab where outbound traffic is completely blocked. Any chance we can get a completely offline version of this?

You can give this a shot, it’ll cache the until you are back home then it’ll upload all of it. Plus it barely uses any battery. https://f-droid.org/en/packages/net.eneiluj.nextcloud.phonetrack/

Migrated from NC to FileBrowser Quantum and its super light weight. https://github.com/gtsteffaniak/filebrowser