Thanks a bunch for the help! Sadly, I must report that the error resolved itself - and I don't exactly know why or how @MikeMcQ : I followed your suggestion and simplified the vhost-config for port 80. After some fiddling (mostly me failing to grasp how webroots and resulting paths work) I had to pause my efforts since other stuff came up. Today - some days later - I resumed troubleshooting, found out what I did wrong (forgot to create the subfolders under the webroot), and it worked as you p...
