There are a lot of these doom-and-gloom scenarios running around. You have to view them through the lenses of strategic value and specific capabilities. These scenarios are designed by major think tanks to just throw a wrench in national capabilities studies and exercises. Think tanks mostly benefit from these discussions getting paid millions to study these scenarios.
GPS I was a weak signal and the closer you got to the ground the easier it is to jam. That is why the military still maintains a specific capability within GPS III.
LORAN was shut down in the 70s and 80s and mostly replaced with LORAN-C for aviation. LORAN-C was scheduled for termination, however, a study (thanks to a think tank) has pressed for an eLORAN capability. The eLORAN has been dropped as specifically named, however, the debate is still ongoing by lawmakers. Meanwhile, the FAA continues its plans to shut down specific VOR stations. https://www.faa.gov/ato/navigation-programs/vor-target-discontinuance-list
The reality is that there is no LRN system, other than IRU/INS, that is going to be immune to interference. With the right equipment on a mobile platform, a bad guy can just as easily jam or redirect a Localizer / Glideslope. Ground-based navigation is not immune to doom-and-gloom scenarios. There is just not a lot of money to study those scenarios.