With the risks to GPS becoming more acute, many jurisdictions are seriously entertaining bringing back a modern version of LORAN.

There's also high frequency firms that want to muscle their way into shortwave frequencies as they can have lower latency between trading sites (eg NYC and Chicago) since the physical infra isn't a direct link as the crow flies (as well as the speed of light being slowed in fiber optic lines). They've even restarted some microwave links, as they don't necessarily need a lot of bandwidth, just latency.