Page regression: What is the best way to mark up an exclusive button group?

### Page URL:

https://lea.verou.me/blog/2022/07/button-group/

### Did this page work in the previous website?

Yes

### What issues do you see?

Broken embed(s)

### Description of issues

Only first Twitter link to advise by @LeonieWatson is shown as link (embed isn’t working), but the following citations are simply missing – not even the links to Twitter are there. 