Leopold FC660M has MX Clear at elitekeyboards.com
Ducky also has MX Clear at mechanicalkeyboard.com
I think you mean QTang. EK doesn't have clears listed.
It's Qtan.
And what are the popular ALPS switches? I know there's the in-production Matias clicky and tactile. What keyboards use these new ones, and what are the popular older ALPS switches? What keyboards use those?
Matias Clicky can be found on the Matias Tactile Pro keyboard and MK.com and Matias sell loose switches.
Matias Quiet can be found on the Matias Quiet Pro keyboard and MK.com and Matias sell loose switches.
I'm a huge fan of the Dell AT101W which has Tactile Black Alps. I also really enjoy the Clicky White Alps which can be found in a Focus FK-2001. Tactile Salmon Alps can be found in Apple AEK keyboards which seem to be very popular.
There's a few boards with complicated blue alps but I can't remember the models at the moment; usually Chicony boards.
I just got a Siig Minitouch with Monterey Blue Alps Variants which I really like.
If you go to the DeskThority Wiki, they'll have a nice listing of boards for switches. If you search for "MX Black", there should be a list of boards that have MX Black switches.