Nowadays, combined GNSS receivers like you mention are available from various electronic retailers for around 20-50$ a piece. The uBlox Neo M8 is a popular chip, there are a few others too. They are widely used in UAVs (where I know them from) and a variety of other applications, and routinely use anywhere between 22-28 active satellites from multiple constellations (compared to typical 7-11 visible for GPS alone).
Re:The GPS wars have begun
by omgtehlion on Sunday December 23, 2018 @06:30AM
(#18745557)
P.S.: the tech was around at least a decade ago. Nowadays you can have at least alternating mode in cheap consumer devices.
The company had no problems selling in the US abd Russia. And even had multiple competitors.
Hence, expert/import laws are not a problem. At least for professional equipment.