A guy came by to buy my old iPad Pro yesterday. After buying an SP4 this summer an initially carrying both, I bought an iPad Mini 4 to be the Surface's companion device instead of the Pro.
Didn't include the HDMI and VGA adapters I have, as those work on the Mini too. Originally bought those for a Mini 1, years ago when they first switched to Lightning. Used through Mini 1, 2, 3, Air 2, Pro, and now Mini 4. And a few iPhones.
Also ordered a Mini DP to HDMI adapter this weekend, for connecting SP4 to monitor at home. I have a Mini DP to HDMI+VGA adapter already, and one to full DP. At work there are devices with a combination of those, so wanted a permanent cable at home. I had both mini HDMI and micro HDMI cables/adapters, but obviously none of those work on the SP4. The MHL to HDMI cable I had I outright threw out this week as I have no devices that use it anymore. Still have ones with microUSB though, so same connector, just not supported. Same as USB OTG, same connector, hit or miss if it works. Luckily some of my devices use mini USB, so don't even have to check if those support it. Same with USB B.... and USB C, actually, as I only have one device with that.
But yeah, Apple is complete shit, with its proprietary connectors and all that. Standards are the way to go. All 11 million of them.