Can both Steam and Epic keys be used?

For the many of us who can't redeem steam keys, is it possible to redeem the Epic key for now and redeem the Steam key later when it becomes available?
I intend to play using Geforce Now, so I assume one of these platforms will be required for GeForce support.

Also GGG, it's kind of iffy for you to not be telling people before they are making their purchase that the steam key is not currently available. Make an announcement pronto guys, and update the shop with a warning.