Aaaand I'm another 13" 2015 MacBook Pro Retina with a keyboard and trackpad that doesn't work.
The SMC reset worked a few times, but now it doesn't work at all. PRAM never worked for me. I've even tried restoring my Mac, which caused me to download several OS versions, none in which worked. The weird thing is that I can put my Mac to sleep via shift + option + command on my internal keyboard, but I can't boot in Safe Mode via shift + power. It's like my keyboard has selective-functioning.
I've seen someone suggest putting the MacBook in an air-tight plastic bag/wrap, and leaving it in the fridge for two hours. I haven't tried that yet, but it seems to be the only thing that's working, if we are all getting this for the same reasons and if it isn't the keyboard connector like the person above me said.