Configuring X login and rich embeds for Discourse

[Lilly]

could be because hosted sites and Meta were fixed recently

Twitter links are no longer oneboxing

I just updated the API keys used on meta, and rebuilt the OP. Tweets now are embedded correctly here (and for clients in our hosting). The issues raised by the OP still apply to self-hosters though. One alternative option here is to load native Twitter embeds, see this theme component.