(sorry for late response, maybe you'll still catch it) There's not a technical problem using multiple GNSS constellations. Officially the US had some treaty wit

(sorry for late response, maybe you'll still catch it) There's not a technical problem using multiple GNSS constellations. Officially the US had some treaty with Russia to allow use of GLONASS as a second constellation. Later on Galileo became the next constellation approved through a civil route, not a treaty. China's BeiDou would have to probably be approved through a treaty since it's run by their military, it's not going to happen. I've been told by someone who used to work at space force that beidou can be used to track users, but that's bullshit with how our receivers use it. Here's a US gov report on the matter, if it's receive only (no messaging component) tracking isn't going to happen https://www.uscc.gov/sites/default/files/Research/Staff%20Report_China%27s%20Alternative%20to%20GPS%20and%20Implications%20for%20the%20United%20States.pdf https://www.uscc.gov/sites/default/files/Research/Staff%20Re... Finally, the way at least Qualcomm receivers work is they will only lock to GPS first and then mix in the other constellations (at least while in CONUS).