I have the Sigma 50mm 1.4 version just before the Art series. While not using this focal length much, it is a really good lens. When I upgraded my Df with the firmware that would allow use of Nikons new "P" lenses, the Sigma became bricked, so I reverted back to the previous firmware. Fast forward a year, and I get a new Z6. The Sigma wont AF on the FTZ adapter, and when I contacted them, they stated that the older 50mm could not be updated to work with the FTZ. But......if I would like I could send it in and they would update it for free to be compatible with the Nikon firmware P lens update. So, I did that, and when it came back, boom, it works with the FTZ as well.
I asked them about it and they said that they never know when doing the updates if it will work with the Z or not, so they never promise it, much less even suggest it "may" work. I found that interesting. Anyway, I am happy to keep the old thing in the stable, and if you have any plder gen Sigmas, I would suggest sending them in for the most current firmware update. You never know what they might work on.