I used Canon AF lenses with the G80, should be no different on the G9. The adapter I used was a Viltrox EF-M43. I used the non focal reducing one and it worked just fine, I had full control over S-AF and aperture, all exif data was present and correct also. Not so good in C-AF. AF speed was a little slower on some lenses than native might be so wouldn't recommend for sports or action. But for portraits, birds in your garden, landscape, casual shooting - you could do a lot worse. Some very cheap EF-S lenses out there
Be warned though, if you wanted to try a focal reducer EF-S lenses don't tend to work because the glass element in the reducer impeded the movemnt on the rear of some lenses like the 55--250 or 10-18mm