Something for semi-private (group or 1:1) chats (rather than public posts), with English-language support, perhaps like Telegram, WhatsApp, etc. Ideally run by a Chinese company (not a US company doing business there or one with US partners like TikTok) with servers, domain etc. in China. I was looking at QQ a while ago but I think their international app version was no longer offered. Wechat is currently closed to registration. Thanks!
You can run your very own Matrix homeserver anywhere, including on a VPS located in China (though this comes with the responsibility of maintenance, and I don't know any Chinese ISPs to recommend offhand.).
There are probably some public homeservers already running there too, though I'm not familliar with any.