Forget "state actors", truck drivers have taken out entire airports with GPS jammers:
* https://www.cnet.com/culture/truck-driver-has-gps-jammer-acc...
People like the Resilient Navigation and Timing Foundation have been trying for years to get some kind of GNSS backup accepted:
China has certainly put their money into resiliency (both navigation and timing):
* https://www.gpsworld.com/china-completes-national-eloran-net...
* https://rntfnd.org//2026/03/19/china-has-built-a-triad-of-sa...
* https://rntfnd.org/2023/11/28/china-eloran-used-for-critical...
Some folks are certainly cluing in: South Korea has (e)Loran and the UK and France are joining up with them:
* https://rntfnd.org/2025/04/30/the-uks-system-of-systems-appr...
* https://rntfnd.org/2025/11/12/s-korea-leads-meeting-with-u-k...
Admittedly, that'll never be of use outside aviation as its line-of-sight only. But if the sun threw a Carrington event (or worse) at us, I think a lot of western aviation could carry on.