Apparently UWB [1] is being touted as the solution to determining indoor location given that BLE and WiFi based on signal strength don't really work well. But development is still ongoing.
I used some Decawave UWB hardware years ago and even in somewhat complicated environments (though walls, multipath, other RF stuff going on) they were accurate within 5-10%.
[1] https://locatify.com/blog/in-practice-precise-indoor-locatio...