@kitten it seems u did find a solution, and probs the better one, all things considered
but it did make me want to point out i have a lil project called TransLoco which is basically self hosted (Apple) Find My or (Google) Find My Devices
although, it has no documentation and only the server stuff is in the repo, i.e no client/app, just some unpublished scripts, MacroDroid macros and iOS shortcuts
@kitten yeahhh, i reworked the MacroDroid macro entirely recently, and there's been some weird bugs (of which is entirely MacroDroid being fucky (iterating through a dictionary will just break in weird ways randomly, but only in the action/function that does the HTTP/API request ))
i do intend to both actually make a proper README with screenshots and everything (recently reworked the UI mostly entirely, so it does look nice and is MD3)
oh and recently added geolocate support, so a device (mostly ones without GPS) can merely send its WiFi hotspots and the server will attempt to geolocate the device with that
devices can also send extra data to be shown in the UI, i.e battery, connect WiFi hotspot, accuracy of location data etc etc
and recently added some multi user support, both for logging in, but also letting others see it devices (albeit everything is defined in a JSON5 file )