Quick summary, probably missing a lot, but...

• Two-ish years ago they decided to sell an overpriced backpack with no warranty. This was criticized considering everything else in the same price/quality categories would have lifetime warranties. This led to Linus Sebastien going on a rant about how warranties are worthless and people should just trust him and that anyone who wanted a warranty was going to threaten his wife (the CFO and one of the major shareholders) were he to die. LMG eventually walked back and provided a pretty good warranty but this is largely considered the "masks off" moment
• One-ish years ago, during a fan tour one of the engineers in Lab (LMG's hardware testing warehouse) criticized Hardware Unboxed and Gamers Nexus with some (actually false) nonsense claims about how LMG do their testing and why it makes them better than everyone else. After this blew up, Linus went on his podcast to say he stands by the engineer.
• Needless to say, GN and HUB took that personally and it led to GN doing one of their industry takedown videos (usually reserved for MSI or ASUS) on LMG with lots of documented examples of downright comedic levels of incompetence in how they review hardware and present results that point toward systemic issues that undermine all the orgs who actually take benchmarking and the like seriously. Look up the video, but it is stuff like not taking the plastic off a mouse (and then complaining about how it feels) or listing complete nonsense numbers for RAM that anyone with half a (computer parts) brain would have said "that can't be right".
• Also, GN pointed out that one of the most egregious examples was the recent one where LMG were sent a prototype GPU cooler and a GPU to review. LMG proceeded to "lose" the card they were sent and use a random different model for the test and then shit on the product endlessly while insisting it doesn't matter that they didn't actually test it because it was a shit product. They then sold the prototype at their convention to an unknown party. All while ghosting the company and ignoring their requests for the prototype back.
• This led to "drama" where Linus, on the LTT Forums, accused Steve (GN) of being biased and a horribly unprofessional reporter for not giving LMG a chance to get ahead of the accusations and insisted they had already addressed all the issues. Which was later revealed to be that they finally replied to the GPU Cooler company literally minutes before Linus posted to gaslight people.
• Also, as part of this, a former employee (Madison) who had left mysteriously spoke out about the sexual harassment and assault she experienced at LMG. This was consistent with vagueposting by other female former staff when referencing their time at LMG.
• The harassment was corroborated by other former staff (one has since recanted after he couldn't find a new job in the kind of blog post that would make even John Xina himself raise an eyebrow) and audio of her manager (James Streib) making stripper jokes to the entire company during the company mandated sexual harassment seminar THE DAY AFTER MADISON QUIT BECAUSE OF SEXUAL HARASSMENT re-surfaced. Streib is still the face of one of the LMG channels.
• This ALSO reminded people of when, OG of Maker Youtube and 3d Printing, Naomi Wu spoke about how Linus had insisted she come to his hotel room at like 3 am if she wanted to do a collaboration and that it made her feel uncomfortable. Allegedly this was all a big misunderstanding and Linus only accidentally removed his wife from the email chain, but Naomi is used to that shit and had much bigger stuff (like the CCP...) to deal with when this was resurfacing.

And just general douche-baggery.

But mostly? It just means to take anything LMG does with a massive grain of salt. They have repeatedly demonstrated that they are not above manipulating their audience and influence to push anti-consumer behavior. So a video where they were "too spicy" for Google for promoting alternatives (some of which LMG themselves operate) is, to quote the children, sus. And yeah, it sounds like the issue has nothing to do with "don't use gmail or youtube" and all to do with "use this random third party app that bypasses all the ads so you can still use youtube".

Other than the stuff already mentioned here, people (probably fairly accurately) thought Linus was a salesman douche with no real knowledge of computers back in the NCIX days.

It was partially true, he was basically a warehouse manager who happened to get lucky making a successful youtube channel which he turned into his own media business after NCIX died.

But that's what the key term is. It's Linus Media Group. Their top goal is to create content that generates views for revenue, and not content that might be useful or takes a lot of effort to do.

Which is why you will almost never see any heavy IT people watching his videos. There are so many examples of people running entire data centers in their house better than LMG could do with actual budget, server space, and hardware. They used to use windows server for everything because they didn't have anyone who knew linux lol.

They’ve been criticized of rushing and skimping on accurate / ethical review practices. There are also allegations that LTT is a fairly toxic work environment, but, the former has more concrete evidence since the janky reviews were recorded and uploaded.

And on a more subjective note, a lot of people aren’t really into the way that Linus behaves on camera. I’m in this camp. I find that he often comes off pretty arrogant and belittling when he’s interacting with his staff on camera.

I actually like those, and started to watch the channel regularly after the house remodeling series.

What's barely sufferable are the "we bought stuff from the internet and here it is. check out our sponsor..." videos that's been published a lot lately.

Also SponsoBlock

Buy second hand or refurbished. Better for the planet, cheaper and you aren't directly giving google anything :)