I saw that ‘source’ too. Pretty laughable.
Here is some debunking of the “Russian forces used a Khinzal hypersonic missile to strike an underground NATO command center, killing up to 300 people including at least 40 high level foreign advisors” story.
https://www.newsweek.com/russia-nato-ukraine-command-center-strike-kinzhal-missile-1791805
https://twitter.com/cossackgundi/status/1648234717739642880
https://www.snopes.com/fact-check/nato-command-center-strike/