Seems this is for One+ and Oppo, but with alt Android OSes like Lineage, would be nice to have it back and available. I'm too dumb to code and prefer not to vibe code it. Unfortunately, I installed lineage almost immediately when I got this phone, and am missing a lot of features I didn't look into until now.

Edit: since this was for Oppo, One+ received capability with an update, making me think this special protocol would work for anyone's device. No special hw required. Maybe there's a way to dump the app/feature files from a ROM to build into an app?

https://www.notebookcheck.net/Free-update-gives-OnePlus-phone-BeaconLink-feature-for-making-calls-without-cellular-signal.953020.0.html