Workaround: Rotate the images and save the .dop files.
Edit the .dop files and replace the value for the orientation by what you need, values can be found on the exiftool homepage. Here’s what they are today:
You can also use exiftool directly to edit the orientation tag.
exiftool -n -orientation=1 20140626-8376.cr2 ; use the values above as needed
Reference: orientation 1 shows all images in landscape orientation. Start from here. It helps to edit a reference image with an easy to recognise local adjustment.
Third option: if there is an .xmp sidecar with an orientation tag…do as above.
Neither PhotoLab nor Lightroom Classic show a change of orientation in history. Keep track of it yourself - and with the help of some text (if any) in the image (or add it yourself as shown above.
More about flip: Does PL8 Elite include the ability to flip? and other threads/posts