I can link and control the GTi through Stellarium. However, at least with my hardware/software set up, there is a conflict between Stellarium and the Synscan app. This is irrespective of whether the mount control is configured to run with either ASCOM or the Synscan app driver.
So, for example, currently I have to do the intial polar aligment visually. The app, particularly the phone app, I found helpful for this and I also sought to fine tune the alignment using the app by doing a two or three star alignment. However, whether it was fine tuning for polar aligment or using the go to function to another star, the mount would never settle down. I could leave it 15 mins and it was still not settled on the star.
Long story short, after hours of frustration, I found that the way that worked for me was to use the mobile app to set up the polar alignment, with the only usb connected being that to my camera for live view. Once that had been done, then I could connect my mount's usb that linked to Stellarium. If the mount's USB was connected whilst aligning, even if it was switched off, the go to function would never settle down.