Use the bloody window
As a fellow ex-OOW (and still a Hydro surveyor) more than one "old man" used to forever shout at the baby bridge teams to "look out the bloody window". People get sucked into staring at a computer screen when closest points of danger could clearly be seen, both in ships and cars.
As for technical kit, AIS, GMDSS, radar, ad nauseum, all these need is a positional feed. Be it GPS, DGPS, Glonass or galileo. it's the lack if a resolved position that causes the alarm, not the fact that a positional feed is out of error budget. Redundancy in systems prevents this, adn you can always hit the alarm cancel button and use a paper chart and a compass...
As for Loran - there's a reason it fell out of fashion. It isn't as good. otherwise we would still use the damn thing, and anyone trying to seriously wreck radio positioning just needs to add a frequency to crash that as well, however they try to enhance it.
Besides, it's not the interference with signals that is the real disaster scenario, it's spoofing. being able to fool systems into calculating a wrong position. And despite Hollywoods (and pinewoods) best efforts, that is actually very difficlut to acheive.
As with every report. Follow the cash. Who paid for it to be written and whats their agenda?