Just out of curiosity I was wondering if it would be possible to update the Z camera firmware in the field with help of an iPad only.
At first sight this looks trivial with the latest iPadOS, just download the firmware file to the download folder and move it to an XQD card in a connected XQD reader.
The caveat is that Nikon firmware comes enclosed in either an .exe (for Windows) or an .dmg (for MacOS) file, both type of files cannot be opened on the iPad by default.
With no suitable utility in sight in the App Store I found a few online file converters that are able to convert the .dmg file into a .zip file. Another issue: the camera firmware is stored in a subdirectory in the .dmg file, most online converters won’t handle that.
The online converter at
https://www.freefileconvert.com however does handle subdirectories, so experiment succeeded.
So the basic flow is:
go to a Nikon website and download the firmware .dmg file in Safari
go to
https://www.freefileconvert.com and upload the downloaded file in step 1, convert it to a .ZIP file and download the resulting .ZIP file.
In the Files app, open the downloaded .ZIP file (it is in de download folder), open it and locate the firmware file
connect an XQD reader, insert a card and move the firmware file to it
transfer the XQD card to the camera, and update the firmware as usual