Got a 'new' iPad about a month ago. It's certainly new to me compared to my old one that couldn't use any iOS beyond 9.something! The new one is actually version 3 model, so it isn't the latest build, but it should last many years, as far as System updates go.
Yesterday, I found a peculiar dialog on my iMac (see attached image). I don't like to install anything just because some dialog says I should, even it is appears to be from Apple!
So, I took a chance and clicked the "Learn More..." button. Sure enough, it opened a page at
Apple Support. It explained with:
If your iPhone, iPad, or iPod touch has a newer version of iOS than is supported by your Mac, you may see [an alert you uploaded to TS]!
OK, it didn't really have the part about TS...
BTW, that page was updated in January 2020, but I think it is at least several years old. There are links to gives about two dozen Apple Support Forum threads going back "two years ago"!
To make a long (dull) story shorter, here is my short (still dull) version.
Despite what the dialog you eventually get says, you will be asked to "trust" the iDevice. Click the "Trust" button and you can then access/backup the new iDevice in iTunes on your Mac. Since my iMac is still using 10.14.6 it is technically not the "newest" version of the Mac OS. The iPad, on the other hand,
is using the latest version of the iOS (14.1). Therefore, there is a "newness" mismatch between the iMac and the iPad. iTunes/Apple know what we have on all our devices. They carefully and often check to make sure we are not trying to 'trick' the Mothership!
The final iTunes/Apple dialog gave me a choice between "Set up a new iPad" or "Restore the iPad". The "Set up" is not the kind you used when you brought the iDevice into he house, however. What it really means is that you tell iTunes/Apple that the iPad/iPhone/iWhatever can be trusted by iTunes/your Mac not to send negative messages about Apple dialogs to TS!
Bottom line: If you get a new iDevice, you may get one of these warnings if
both your Mac
and the iDevice don't have the "latest" OS.
You must trust Apple to know what is best for their hardware! 
Or else!
