What are some of these platforms? Would love to know

I get the feeling whatever I provide is going to be criticised, regardless, here goes:

百度贴吧 - https://tieba.baidu.com/

Probably the biggest platform out there. You can argue it's censored but then again the same arguments could be made about plenty of Western platforms who follow the moral mores of 2021. There's a lot of leetspeak to get around filters when talking about sensitive topics, translations aren't always great but if you find something particularly out of place maybe try checking for alt meanings.

There's >300 million active monthly users. Plenty of things you won't like in there.

人人 - https://www.renren.com/

Facebook style, mostly younger people.

天涯 - http://www.tianya.cn/

Traditional type forum, mainly older people, certainly more patriotic.

If you want to only read opinions you are more amenable to and won't accuse of being bots/cybertroopers I'd suggest the forums that foreign mainlanders often use. Around East Asia and the bamboo network there's few popular places:

吹水台 - https://lihkg.com/

Cari, an example thread - https://cn.cari.com.my/forum.php?mod=viewthread&tid=4263651&...

Plenty I've missed surely.

What's the best way to keep up with modern Chinese culture for someone in the Anglosphere? Is Avocado Toast a big thing among millennials in China? Is there (was there) any Hipster movement in China? To what extent does Western culture penetrate China and what are the latest fads or fashions?

Maybe you could watch their TV and movies? I've lived outside my country of birth for most of my life, so that's how I learned about American culture before moving there.

Of course after arriving, I realized that a lot of what I saw is either aspirational or realistic only for a very small cross-section of American people.

Would love to hear examples of other platforms.