I'm sure I had that blank screen problem before but it wasn't blank. I plugged it into a monitor and the screen showed up there. As is was set to second display only after update for some reason. Think it's due to aspect ratio being portrait rather than landscape.
Lenovo released a new BIOS update, N3CN42WW, for the original Legion Go around two months ago, and it seems that it is causing serious issues for some users.