do you also have issue with opening HDRI in Blender 2.8 release candidate? Did something changed? My approach is to go to the world settings, change color to an environment texture, click to open texture, but all HDRIs are invisible for Blender. I tried switch off filters or move HDRI directly to the world window, but nothing happens. I checked also addons, did I miss something?
That's weird, but when I copied HDRI to different folder then it works. Even HDRIs in previous folder are visible.