Add me to the long list of users who've experienced this issue.
Screen freezes completely, trackpad loses all sort of responsiveness, only thing to do is to hard reboot.
The first time it happened I was just browsing in chrome.
And it happened about 3 more times, all of them watching youtube videos (fullscreen and non) in chrome.
There seems to be a pattern here...from the comments I've seen it's almost always when a browser is open and most of the time is performing some sort of gpu work (like videos)... but the fact that the 'crash' completely disables and 'turns off' the trackpad, I'm thinking this is not just a issue at the application level. It's probably some really low level kernel issue that has either to do with the gpu or as some have commented, with the t2 chip.
So basically, it's not sure if this is gonna be solvable, but IT'S BAD.
Anyways, I'm about to install Mojave right now, I hope they did some magic.