There are 2 drivers you can try: Downloads for Intel® HD Graphics for Intel Atom® Processor Z3700 Series
Unfortunately your rig is not supported under Windows 10 by Acer according to this list: www.acer.com/ac/en/US/content/windows10-fall-creators-update
Oddly Acer offers a BIOS that "resolves Win10 brightness issue": www.acer.com/ac/en/US/content/support-product/5150?b=1
I don't know if a BIOS update fixes your issue, but as usual BIOS flashing is at your own risk.
Thanks Stefan for your reply. Tried this, but I get the error "The driver being installed is not validated for this computer"
So I then tried to find and install a generic driver.... turns out that that was already wht your were giving me.
So that finally worked when installing from the driver window from device mgt (instead of just running the exe file)
But, no change in behavior... Kind of disappointed in Acer and Intel and windows I guess: that a version updat like this can end the usability of a laptop only 3 years old because I cannot add an external display anymore....