Apple DTK, how long did it take to get an approval?
I’m not going to report anything about specifics here due to NDA but I would recommend everyone assume Apple has multiple queues and waves of hardware to build. Asking Apple directly or discussing the DTK on the private boards Apple has for DTK is the best way to get actual experience and not guess work or people gaslighting you that don’t have first hand experience.
I would apply direct to Apple and then wait or contact Apple via developer support after a couple weeks minimum.

https://developer.apple.com/programs/universal/

There’s not much you need the DTK for today so build your app and ship updates. Having apps love in the store is the best way I know to get priority for limited resources. Along the way you can open a developer support if you have specific compatibility concerns as you encounter them.