That was a great hint, thanks!
The script shows the selection dialogue as expected if I run it through script editor. If I instead run the same script by clicking on the entry in DT’s script menu, nothing happens. Will try some stuff and report back if something solves it.
// Edit: It’s working now in DT! In case it helps someone, these are the steps that seem to have worked:
Apparently homebrew does not always automatically install applications to the usr/local/bin path - however, this is the path referenced in the script. After not finding Exiftool there although it was already installed, I found it in my homebrew install directory and changed the path in the script accordingly. Then, after running the script through Script Editor once and then trying again in DT, I got the below message and confirmed. It’s now fully functional - looking forward to further testing.