I've been using Particle with the new YT design for months, unil today. Where did it go and why?

UPD. Iridium. Yes. Great addon! I don't understand how it got deleted from my browser. At first, I thought that it happened because Greasemonkey was updated to be compatible with Quantum, but now I'm not sure.

UPD. It was really about Greasemonkey. I've downloaded js from Github and loaded with Tampermonkey, enabling Material again (hard to find how to, when it was once disabled). But, now it's working again for me. Yay!

Btw, Greasemonkey's devs suggest script writers to update their scripts for the new GM version, cause there's no backward compatibility in it: https://www.greasespot.net/2017/09/greasemonkey-4-announcement.html