I’ve answered this question for someone else in the context of tracking luggage. Your use case is also one that the branded apple airtags are best at.
If you want a big headache project that doesn’t work then try anything but airtags.
Theres an android find my app and you can run it in a container in graphene.
If you want a quick, simple, functional solution to your problem then bite the bullet and use airtags.
You, uh, also maybe shouldn’t be asking for “privacy respecting” electronic tracking devices. The application is fundamentally not private and cannot respect privacy by design.



Hey I do meshtastic and tried it for object detection and used a homemade beeper and an off the shelf tile beeper and I ended up going to airtags instead.
You really will be better served by just using airtags.
If you can be clear about what kind of privacy invasion you’re trying to avoid I can help you figure out how to make that work.