Love Gigapixel AI. It works flawlessly. I always export any photos I want to re-size from Lightroom as a TIF. I then open the photo in Photoshop CC 2020 and run the Gigapixel plug-in and save the resized image as a TIFF. This has always worked fine.
This morning I was prompted to install an update. After installing the update to ver 5.1.1.
I have the option to save to TIFF but even selecting the file to be saved as a TIFF, TIF or DNG the saved file is a JPG.