@JonathanAllan I implemented Ðe and Ðo like that because that's how ¦ is implemented. If they weren't implemented like that it might be hard to do something like this but maybe it would be worth having a one byte €¦ as well
Jelly, 5 bytes
ṙÐe20
Try it online!
How?
Fix every other card and intersperse it with a rotation of the deck left by 20 places (18 and 22 places also work; furthermore so does either direction of rotation as well as fixing either odd or even cards)