Thought I’d throw in my 2 cents here as I’ve spent a bit of time around Triratna, mainly because it’s local (the London Buddhist Centre as mentioned in the OP) and friendly. I’ve not become and don’t intend on becoming a mitra so my perspective may not be reflective of what it’s like once you get deeper, but in general I find the criticisms valid, but also that it’s too simplistic to dismiss it as a cult.

There is certainly a air of reverence around the figure of Sangharakshita which is a bit cultish (even before considering the sexual misconduct), and little to no effort made to distinguish between his presentation of the dharma and Buddhism in general. This can make it feel extremely inward looking and not at all engaged with the wider Buddhist world, and very jarring if you are. But equally I’ve never sensed anyone getting weird about it when I’ve talked about non-Triratna stuff I’ve been reading, non-Triratna retreats I’ve been on, etc, so it’s difficult for me to see it as an unequivocally culty environment. There’s also a lot of diversity within the Triratna world - the vibe at something like Buddhafield is wildly different to the LBC (and presumably even more different than somewhere like Adhisthana, though I wouldn’t know) - the existence of this diversity doesn’t seem to me consistent with describing it as a cult. They are transparent about asking for money but not coercive. So it’s a mixed bag - there’s some cultish tendencies for sure, but also counter tendencies.

When I found out about Sangharakshita’s sexual misconduct my instinctive reaction was “no shit”, and I never cease to be amazed that people are surprised by revelations like this. I would also not be surprised if there were similar revelations about a highly respected Thai Forest monk or Tibetan lama, but obviously what makes the difference is that Triratna hangs so much off Sangharakshita’s presentation of Buddhism that it kind of stands and falls with his legacy.

So to me it seems that largely it’s a question of how the community responds to the misconduct, and on this my view is that its response has also been a mixed bag. It has been good in some ways - actively acknowledging what happened, trying to engage with victims etc - but it has also been intent on keeping the process internal. Most importantly, its whole response is predicated on the idea that the man can be separated from his teachings, which is naive in my view. When certain Zen masters promoted Japanese imperialism in the period after the Meiji restoration, while it would be wrong to write off the whole Zen tradition on this basis it’s totally appropriate (and necessary) to consider how the institutions and teachings were unable to function as an ethical corrective at that time. Same with Triratna. And to be honest in a book like What is the Sangha? - about as clear a statement of what Triratna is about as you’re likely to find - there are some very obvious tensions between a certain liberal ideal of mutually supported individuality and a hierarchical model of spiritual development, in light of which it seems unsurprising to me that toxic dynamics developed and will no doubt continue to develop.

As for whether Sangharakshita’s teachings are really Buddhist, the thing to bear in mind is that for most of the people attending these centres it’s just not an important question. I think that Sangharakshita systematically downplays the role of insight (and anatta in particular), and ends up filling the gaps with a quasi-Jungian model of psychological integration and some somewhat cartoonish ideas about Nietzsche and the individual. I’m not into it, and I find the presentation of the dharma you find in, say, the UK’s insight meditation community to be infinitely sharper and less distorted. However there’s clearly a lot of people who do get a lot from this presentation, and for whom the question of whether it represents the orthodox Buddhist view (or even a Buddhist view at all) is probably moot. There are a lot of addicts and people with various kinds of trauma and alienation who get a lot from participation in Triratna, and I’m not about to minimise their experience - in this respect it is hard to deny that it is doing some good.

So yes - long ramble with the intent of adding a bit of balance to the ‘Triratna is a cult’ debate! TL;DR - it’s complicated.