I have a site for which Cache Everything is set.
When Mirage is also enabled for this site, it seems the CDN no longer returns the cf-cache-status header indicating if pages are a hit/miss.
Is this expected behaviour? Is there an alternate way to determine if we’re getting cache hits?
No, this is not the expected behavior. You should see a cf-cache header when Mirage is enabled.
Cache everything should not impact the caching of images, only of generated HTML pages, which are not cacheable by default and will only be cached via page rule.
Are you seeing any error messages when you visit your site with Developer Mode on?