Yeah, what’s left of the surround looks to be foam – notorious for disintegration.
Here’s the link in my previous post exposed: https://techtalk.parts-express.com/forum/tech-talk-forum/65083-infinity-video-1-center-channel-refoam-repair-or-replace
The 5th post down describes what one guy did with the same speaker you have, and the replacements are still available.