This is the YouTuber – https://www.youtube.com/user/AllardJason. It sounds like his current projects involve Abandoned from Above which is a much safer project than urban exploring from the ground. It’s worth noting that someone owns the property and may not take kindly for someone to be exploring it without permission. I know one YouTuber who did this and has not been seen for a while. It’s believed he happened on something he should not have seen or may have been injured without recourse to getting medical aid.
This can happen in a place that allows exploring. I saw an article where a person was stuck in a small crawl space and he died as a result. There were plenty of people in the area who tried to help him, but they couldn’t free him from the crawl space.
I tried to find videos where he was not trespassing or using aerial photography to visit places. I did include some where he may have been urban exploring on the ground.
I would always seek permission first before exploring anything abandoned. I have read about people being injured due to unsafe building conditions. Thankfully, they had someone able to call for help or assist them to a hospital for treatment.
I know one abandoned missile silo has been gated to avoid people having problems exploring it. It’s full of rusty stuff, possibly deep water, unsafe areas that may collapse if you walk on them, and areas where you may find yourself needing help. That’s not counting the asbestos problems and carcinogenic materials issues used in building the missile silo.