I’m just going to go with the scenario of ‘the specific part of the EM spectrum that we use for comms is no longer accessible to us’.

So, mobile data and GPS are out. A heck of a lot of people suddenly get very lost, and the immediate aftermath would include a lot of car crashes- mostly from people trying to play with their phone while driving, or just generally being distracted. Long term, people would get used to having to find themselves on a map. I doubt street directories would make a comeback, as it’s relatively straightforward to download a map to a phone by plugging it into to a computer, or USB to Ethernet. Oh, in that regard- The shortage of USB to Ethernet adaptors would probably hit before the toilet paper shortage.

There’s a large portion of the world’s population who like to stay inside and listen to the radio or watch TV, the internet still being an unwieldy thing that the yung’uns use. These people will start getting their entertainment and news by walking outside and congregating - At least until they get a computer or phone setup wired. Hopefully, many will continue to go for walks around town to see their friends and eat a meal. A lot of households are going to have a whole lot of Ethernet cables run all over the floor for quite some time. People will start buying switches and routers to get more outlets next to the couch, for example.

Massive queues will form around the few existing payphones, until businesses and homes at central locations will start offering up ethernet ports. Because this started soon after the Blackout, rooted in generosity and helpfulness, this will just become a free service.

Taxi drivers will start congregating at these spots, plugging in and updating their location, moving to other locations where there is few drivers- and hoping that others aren’t getting the same idea, unable to know that until they arrive. The old guard of taxi drivers, who worked pre-Uber and have an encyclopedic knowledge of the local streets are in high demand, and people seek them out.

A lot of scientists are out of a job. People who worked with radio astronomy are suddenly having to peer through optical telescopes again, and keep talking about the good old days. Whole divisions of people at space agencies, responsible for things like monitoring and control of satellites, space probes, and rovers are suddenly retasked to creating ways to create autonomous return probes to find out what the fuck just happened. Some start trying to work out ways to replace radio by using giant scaled up versions of television remote controls, putting giant infrared lights on mobile phone towers, with smaller repeaters on top of houses and cars. (For funsies, I’m assuming point to point microwave comms are out- which has the implication that microwave ovens don’t work any more, with the associated knock on effects of house fires from people melting microwave dinners in ancient, unmaintained conventional ovens).

People who worked with wireless stuff- from FM radio DJs to antenna design engineers are all out of work. Perhaps they start selling coffee to people stopping by those public ethernet locations? Unfortunately, there’s a noticeable economic downturn from so many vacant jobs, people being out of work suddenly, and commerce becoming so much more difficult. Cash becomes much more useful, and those handy dandy wireless payment terminals don’t work so good anymore, and while waiting for wired replacement terminals to arrive, people get used to cash again. There’s a knock on effect of people keeping cash to themselves, despite the government being almost completely unchanged. This downturn, along with jobs that don’t exist any more, puts a lot of people out of work. However, they are likely to start filling the jobs left vacant by the thousands of people who perished in the utter chaos that was every aircraft on the planet trying to land at the same time in utter confusion.

A couple might make it safely down, but it only takes one accident- say a little Cessna coming in low, not seeing the 747 coming in faster from above, to turn the runway into a total mess of burning jet fuel, wreckage, and stunned people slowly bleeding out, surrounded by smashed bodies and assorted socks. Aircraft block major highways attempting to use them as runways, often causing huge multi-car pileups by giving already already distracted drivers a totally insane thing to have to deal with. Many pilots take the opportunity to ‘do a Sully’. Hundreds die as waterways around major airports become congested with crashed aircraft, with many potential rescue personnel sleeping through the whole thing, because who the heck has their landline phone number, even if they have an actual phone plugged into the wall?

In short, I’d watch that movie. Maybe a series in three parts, immediate, a few months later, and then years after. Great question OP, thanks!

Oh, also- people who made special effort to get a phone that has a headphone jack will be smug as fuck for a very long time.