Hey, I've had the same issue as you guys. My trackpad stopped working overnight without doing any update or installing new software. I looked on forums to try to find a solution. Restarting the Mac didn't work even temporarily, neither did to put the Mac on sleep mode for 2 minutes after a restart.
My problem is now fixed.
I updated my MacBook Pro (Retina Early 2015) to BigSur 11.6.1 (was on 11.3 or 11.6 I think), and everything went back to normal. I can't tell you if it's the new version that fixed it, or just something that the Mac did by itself when it was updating, but I'm happy it's back!
Just to let you know, I didn't try any of the NVRAM/PRAM or SMC reset, nor Safe Mode or manual power off.
William-Harvey
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