I am trying to get a developer site up and running that uses SSL only with 3 web applications that use SNI. Everything except "openwith explorer"
The error I get is:
We're having a problem opening this location in File Explorer. Add this web site to your Trusted Sites list and try again.
Doing what was suggested in the error message had no effect on the symptoms.
UPDATE:
A production system that had the Web Applications created using HTTP and later had HTTPS with SNI added, work perfectly over SSL. The original Farm mentioned in my question was a development environment where we created the Web Applications/root sites using SSL only. That's the only important distinction between the two systems.