One that's been prolific is the idea that 5G causes Covid-19. As we've pointed out before, this is as non-sensical as saying the radio causes super gonorrhea or Tom Cruise causes bread. Covid-19 is caused by the virus SARS-CoV-2, which you can even take a look at for yourselves. Conspiracy theories about 5G actually extend back a lot further than the pandemic, for instance, easily-debunked claims that 5G had caused a mass bird death incident in the Netherlands in 2018 when in reality there weren't even 5G tests in the vicinity at that time.
Some unscrupulous people have clearly decided to take advantage of the conspiracy theories surrounding 5G and Covid in order to make a quick buck. As well as people selling "cures" for the virus (spoiler: if there was a proven cure we would all have heard about it, not just some dodgy website you found on Ask Jeeves), some people have started selling products to "protect" you from 5G.
People on Amazon are selling Faraday router shields or guards to place over your Wi-Fi router to block 5G.
Faraday cages are an enclosure made of a mesh of conductive metals designed to protect electronic equipment from external interference, eg from electromagnetic radiation. Check out this cool video for a demonstration.
Or this even more awesome video of a Faraday suit.
While Faraday suits and cages are awesome for powerline technicians who want to remain not dead, and really, really cool to demonstrate in front of tesla coils, they are the last thing you want to place over a Wi-Fi router, as a lot of conspiracy theorists are now discovering.
Customers that have bought these Faraday cages have also left angry reviews when it turned out they performed like a Faraday cage. Underneath one product that sells itself as "Large WiFi Router Guard (Blocks About 90% of WiFi Router EMF While You can Still use The Router) Blocks 5G!" there are a fair few verified purchasers who have complained about how they're now radiation AND Wi-Fi-free.
"The box does work at keeping radiation in but also Wi-Fi will not work unless you're in same room as router! It decreases the signal by 90%!!" one reviewer wrote. "We really wanted to like it but it was impossible to use our phones in any other room in the house. Also the seller keeps the shipping fee $25 so that was annoying."
If you're wondering whether the sellers believe the conspiracy or are just making a buck off those who do, one of the sellers left a pretty conclusive clue.