What are you looking for OP?
Permission/reassurance to sleep train? Just pick a method that sounds fine to you and try it. It doesn't cause attachment issues, this is nonsense. And I say that as somebody who has never sleep trained and probably never will. Attachment issues are not caused by one off things like sleep training, they are a picture of the general responsiveness to the child across the whole childhood. Neglect causes attachment issues, not sleep training as a one off within a full picture of a loving, responsive relationship.
Most of the criticism of sleep training from a more attachment parenting perspective is that it's not necessary or the "only" option (unlike what a lot of "experts" will claim), you don't have to do it if you don't want to, and pointing out that as an idea, it doesn't really match/mesh very well with a generally attachment-supportive parenting style, which is not the same thing as saying it causes attachment issues, though the internet seems a bit confused on this point (and any nuance in general, TBH)
Are you looking for a fight? You seem very defensive against anybody who does think it causes issues.
Gabor Mate is a quack BTW. Lots of unsubstantiated pseudoscience coming from him. Not saying he doesn't do any good work but some of the stuff he says is highly questionable.
What it is useful to know and I think never really gets talked about on either side is that children respond differently to sleep training. Some of them respond very quickly and cry very little. This seems to be the poster child for a positive sleep training experience, and there's no way this kind of experience is causing any harm. Some take a little longer to respond and cry a little bit more, but nothing extreme. A few weeks/up to an hour or so of crying. Probably distressing, although temporary. But some just don't respond at all, they get more and more distressed. Most people wouldn't continue in that case, but it's possible that continuing if your baby is like that could cause some kind of harm even if only short term.
But I think that might be part of what causes the polarisation? Pro sleep trainers thinking that the babies in the third category don't exist and they are really in the second one and the parents just needed to persist a bit longer, anti sleep trainers not really realising that the first category exists and imagining weeks of anguish before the baby sleeps/thinking all sleep training is like the horror stories of babies being left for hours in their own vomit or scenarios like Romanian orphanages, and being upset by that whether it causes lasting harm or not (and that kind of extreme probably would TBH).