I use this lens on my GH5 for professional video and photo jobs. For the price I was very disappointed, just buy the sigma 16mm if price is an issue for you.
Out of all my lenses this is by far the worse at auto focusing. I know the wider field of view makes it harder because there are so many things in the frame to focus on but it's just unusable. It also looks worse than other lenses when "hunting" for the subject.
I've used it for two photo shoots so far. When the model is back lit their hair looks purple from the chromatic aberration. It does the same thing when shooting video.
The build quality is great and the design matches perfectly with the GH5. I love having the aperature dial on the lens, although it does get moved by accident on occasion.
If You're like me and want that 24mm look and low light capability than you don't have many options. Overall this lens is good. It should be priced around the $800 range. The product was advertised as new but it was not. The box was in terrible condition and all scratched up. Everything had already been opened (buy from another seller if possible).