Don't know where this stands today. I just upgraded to 2022.2.2 only to discover this problem which broke several of my control pages.
One point I wanted to add was that I have several pages where I use this function to show an image dynamically. In my case, this means that I show a picture from my Doorbird (in one example) as an overlay to my control page when someone hits the doorbell. The image from Doorbird is a .jpg. After buzzing them in, I want to make the picture disappear. Since .jpg images don't have a transparency layer, I need to replace the image with a .png file when I want to make it "disappear". Without the dynamic URL function, this is very difficult to achieve. The file:/// has to point to a .jpg file or a .png file but I had been swapping them out with indirection through a variable. I can't get a png from Doorbird and I can't make a transparent .jpg.
Hoping the dynamic URL comes back soon