As a workaround, at the moment we’re just doing something along the lines of:
twttr.widgets.createTweet(tweetId, container, function (widget) {
var links = widget.shadowRoot.querySelectorAll('a');
for (var link of links) {
link.target = '_blank';
link.rel = 'noreferrer';
}
});
(apologies for errors, I just typed this out by hand)