This claim is technically true but is very over exaggerated. Most people would be putting their health and safety at risk and could end up in the hospital. Even if you are properly trained for a marathon you could end up in the hospital though much more unlikely. 
The marathon handbook states that they have seen people posting on Tik Tok running a marathon with no training as kind of like a trend and while they were able to complete it others might not be so lucky they say "You may be able to walk a marathon or jog/walk a six- or seven-hour marathon with little to no training, but if you’re hoping to run a four-hour marathon and complete the whole way, you are setting yourself up for a high risk of injury, muscle soreness, and disappointment, if not worse." Everyone is different and some people are able to do it without training and with little pain or injury while others could be disastrous.
The hoag.oc marathon running festival states that "During the race, the repetitive impact of each stride can place immense strain on unconditioned muscles, exacerbating the risk of strain." they claim that any of the muscles in your legs could get strained if you run without training.
My last source the marathon handbook states that a former D1 athlete said "After standing up, walking out of the tent, and heading out to get picked up, I experienced probably some of the worst pain I’ve ever felt in my lower body. Moving at a snail’s pace, every step hurt from my feet all the way up to my hips." Even someone who is an athlete but out of their sport and conditioning for a while had a very hard time. 
In conclusion it's technically true/ possible but it is highly discouraged and not recommended at all.
https://marathonhandbook.com/running-a-marathon-without-training/
https://ocmarathon.com/can-you-run-a-marathon-without-training-2/
https://www.outsideonline.com/health/training-performance/no-training-marathon/