I am trying to run Wordpress on an Apache httpd server as an http (port 80) service behind a proxy that uses https (port 443). This is similar to the situation discussed in
Most of the URLs are transformed properly but I get mixed content errors from files associated with the twentyseventeen theme.
"Mixed Content: The page at 'https://testwp.artifact-software.com/' was loaded over HTTPS, but requested an insecure stylesheet 'http://testwp.artifact-software.com/wp-content/themes/twentyseventeen/style.css?ver=4.9.6'"
It looks like the function creating the URLs related to the the theme is not looking at the site url to get the https:// part.
1) Is this an error in Wordpress or in the theme?
2) If it is the theme, are there themes that are known to work in this situation.