Looks like you solved the problem with a lot more effort than it should have taken due to my braindeadness.
I installed the Intel HD graphics driver 9.17.10.2828 from the Acer site and it worked!
What threw me off was that they labeled it "VGA" drivers and I thought it was only for the VGA...as if it was a separate controller. So I never thought to try this driver. Then I noticed the version number is in the format of the other Intel HD drivers. Why did they do that instead of just calling it Graphics Driver or something???
I reinstalled the OS from scracth again and tested.
So summary:
On Windows 10 1803, Intel HD 9.17.10.4459 works.
On Windows 10 1903, Intel HD 9.17.10.4459 does not work.
On Windows 10 1903, Intel HD 9.17.10.2828 works.
So apparantly, for my particular HDMI display...whatever chip it uses causes the 1903 to bomb out and lose the display using the up to date Intel HD drivers.
I'm wondering, should I try to install different Intel HD drivers in between those versions (I assume there are some). Perhaps Acer might have discontinued the product so they never updated it past
9.17.10.2828... Or that they knew the Card Reader wouldn't work so they never bothered with Windows 10?