The createTweet network request seems a bit difficult to reverse engineer, but I gave this a shot by using the formally provided solution at https://publish.twitter.com/. By including the tweet's user, you can just construct markup and let twttr.load() pick it up. The minimal markup seems to be `<blockquote><a href="https://twitter.com/${user}/status/${id}"></a></blockquote>`, after which `twttr.load()` seems to load and fill it in.
Unfortunately, it requires the user as well, so although it's *a* solution, it's not exactly a *good* solution since it won't be backward compatible. See: https://observablehq.com/compare/bb2055d580bbbab2@82...8d0464cb5b263365@116
The card is not showing up for me in Chrome 93/94 (Firefox works fine). Seems that the iframe height is never updated and stuck at 0 unless the iframe element's size is changed. E.g., adding a rule `iframe {min-height:1px}` via dev tools or within a cell will immediately trigger an update of the iframe's inline style.
Access to XMLHttpRequest at 'https://cdn.syndication.twimg.com/tweet-result?' from origin 'https://platform.twitter.com' has been blocked by CORS policy: The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'.