This is my best summary, it is long so sorry about that but there's a lot to it.

Linus is probably the largest tech youtuber there is.

He's been rapidly expanding his company, building out a full lab that is trying to rigorously test products (mostly in an automated way) so that consumers can have confidence that a $50 power supply isn't going to shit the bed, or that this GPU will get you the same performance in these games at this resolution so save your money, etc.

The initial controversy is that they have issue with the automated testing where results were often super wrong and that slipped it's way to multiple videos and instead of taking the videos down and correcting them, they left them up and just had a little text graphic over the video with the correction. Many youtubers do that kind of post video correction, but LTT does it a lot. Additionally they tested an $800 prototype watercooler on a 4090 when it was built only for a 3090ti which pretty much invalidates the entire test, but they still gave a conclusion that the watercooler sucked and was a bad product. That could tank that company. They did not bother re-testing with the proper GPU because Linus felt no one should buy an $800 watercooler block anyway. Additionally(x2) they reviewed a mouse and said it was terrible because the glide was really bad. Turns out there were protective stickers on the mouse feet that needed to be removed. They took multiple days to correct the video and by that point the damage was done.

The second controversy is around a Madison (former employee) where she received tons of verbal abuse, degradation, from various LMG employees/management and some even sexual harassment. There was a lot of hand-waving of her raising those complaints as "causing drama" and to "calm your tits" and other various things. She suffered a lot mentally from it and even "cut her own leg" just to go to the ER to have a day off. Her write up is pretty long and fairly brutal.

I think a large part of the issue is everyone is incredibly overworked at that company and crunching every day to release as much content as possible which leads to a fuck ton of errors, very heated and emotionally charged employees and lack of oversight over serious issues. Couple that with rapid expansion of employees without a functional HR (I think someone was hired recently) and the vast majority of people effectively "learning on the job" how to be a manager, director, leader, etc. and it's just an explosion waiting to happen. And it has exploded quite spectacularly.

I'll be curious to see if they turn it around and also what comes from the outside investigation.