When I first installed 16.04 about a year ago the keyboard worked straight out of the box. Somewhere around October or November it didn't work anymore. I am not sure when or if it was caused by an update because I simply didn't use the tablet much.
Last night I reflashed to stock Android and the keyboard is now working. Interestingly, the keyboard has some issues in Firefox but the keyboard is functional in Brave Browser, Mobi Office Suite, all Google apps and others.