Apologizing in advance for a goofy answer...
I have a first-generation iPad rocking iOS 5.1.1 and a first-generation iPad Pro 12.9-inch on *iPadOS 15.2 beta. The Pro gets all the usage, 1000%.
But then to use the original I'd need to find a 30-pin cable and hope the battery can actually hold a charge. But it still works great for black screen work. Love the huge bezel, the square in the middle of the Home button is totally to die for (and none of that creepy Touch ID to worry about). Oh, and the camera... well, the 30-pin Camera Adapter.
Pop quiz: How many more cameras does iPhone 13 Pro have than that first-gen iPad?
Hey, I found a 30-pin to USB-A cable while looking for the Camera Adapter! Wish me luck! At least the battery hasn't expanded. Yet.
Hmmm, not booting. Think it's a bad cable? Hope not, there's no freakin' chance I've got another one of those things kicking around.
OMG, I see an Apple logo!
Boot loop
Wow, a blue iTunes logo on the Recovery Mode screen. Now that takes me back!
No, not going to try to restore it in Finder. At least, not tonight.
I wonder if Apple is still serving-up the 5.1.1 IPSW?
And is it any surprise that if I disconnect from charger it doesn't even boot loop? Lousy battery life, planned obsolescence, yada, yada. Ya think a nearly-12-year-old Tesla with original batteries would start up?
So at the end of 7 innings the score remains first-gen iPad Pro 12.9-inch 1000%, first-gen iPad 0%
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* Damn, I skipped right past iPadOS 15.1.1 and didn't even realize I was passing the exactly-10-major-versions milestone. It's exactly the gap between Snow Leopard and Big Sur! Boy, time flies when you're having fun. Then again, my Early 2008 iMac came with Leopard. Imagine if that iMac was like that original iPad (shipped with iOS 3.2, maximum iOS 5.1.1). The maximum OS X it could run would have been Lion! Meantime, that Pro came with iOS 9.1... so we're six major versions along. Original iPad got 2 major versions (iOS 3.2 to iOS 5.1.1), just like the original iPhone (iOS 1.0 - iOS 3.1.3). And people complain that they can't update iPhone 6 (which started with iOS 8.0) beyond iOS 12.5.4. Kids these days! They don't know how good they have it! And then there's iPhone 6s. 6s has run the gamut from iOS 9 to iOS 15.x (are you noticing a trend here, people?).