It is not my experience that keyboards are part of their garden wall. I have used bluetooth keyboards with my iPads going back to the first generation of iPad Mini.

What their keyboards do offer is tighter integration. That’s not a wall, it’s more like growing enticing apples in the orchard within the garden.

Not much different than the situation with upgrades for my Volvo. The Volvo stuff is tightly integrated. OEM stuff sometimes involves compromises, like plugging things into the port and fiddling with bluetooth.

I'm not sure what you're getting at here, bluetooth & USB keyboards all work fine. I've used aftermarket keyboards exclusively for the past... 6 or so years on the iPad.

You can use any Bluetooth keyboard with it.

And I’ll bet my Bluetooth trackpad works with this now too.

To follow up, yes, it does. But because iPadOS doesn’t support all the swipe gestures on my first generation Magic Trackpad that my Mac does—notably scrolling—I’m disconnecting it. If I’m going to have to touch the screen to scroll, why have the cursor?

Standard bluetooth mice already work, they've just buried mouse/trackpad support under the accessibility settings in iOS13.

It probably does. I have a $20 no-name Bluetooth KB + Trackpad. It works perfectly with the current iPadOS.