An issue that's becoming more and more problematic is third party compatibility. With each new firmware update or camera release, it seems that many third party battery, flash, and lens products suddenly stop working.
Yes, I know the conspiracy theory is that Nikon does this on purpose, hoping to stop third party products from eating away at sales of Nikon ones. I've not known that to be true, though. In every instance I've been able to verify, Nikon was simply adding features, or dialing in specific performance (focus) and safety parameters (batteries).
In a couple of cases, these changes have impacting Nikon products. For instance, some original EN-EL15 (no letter) batteries won't work in the Zf camera (and I suspect will stop working in future cameras and maybe even firmware updates). The reason for the change that caused that incompatibility appears to be a safety issue.
Both the flash hot shoe and the lens mount have very sophisticated communication protocols. First off, the timing of communications is very specific and precise, and I've noticed that some third party vendors of flash units are not seeing that correctly. Second, any value found to be out of range—and Nikon sometimes tweaks the range to keep spurious values from altering performance—will essentially make the camera stop responding to the device.
In the lens mount communications, there is a call/receive protocol involved, where the camera is querying the lens about its capabilities and state. If an out of expected range response happens, the camera will put up the incompatible lens message and refuse to operate.
The companies that have the words "licensed from Nikon..." in their materials generally don't have these issues, because they've entered into an agreement with Nikon that allows the cameras to recognize those devices (typically lenses at this point, but also recent Nissin and Profoto flashes).
Most of the Chinese lens makers don't seem to be getting Nikon licenses. So what happens is that a lens that's been out and about for awhile, say the Yongnuo 85mm f/1.8, will get posts that say "it works" appearing on the Internet and then a new camera such as the Zf comes out, and guess what? The lens won't work on it. We've been down that street before, where the third party lens makers are reverse engineering lens mount communications, and not aware of a particular value or change that the camera maker was about to implement.
I guess that my advice here would be this: don't buy anything from a third party vendor who doesn't have the ability to update the firmware in their product and doesn't have a track record of doing that in a timely manner. I have one lens, for instance, that requires a firmware update to work with my recent Z cameras, but which I can't install because I'm a macOS user.
As a reminder, these are probably the "safe" products at the moment (Nikon licensee):
- Profoto (flash)
- Nissin (flash)
- Cosina/Voigtlander (lenses)
- Sigma (Z-mount lenses)
- Tamron (Z-mount lenses)
