What a headache. I mean I guess on the one hand this is a minor victory for people like me who prefer Universes Within cards. But on the other hand, I think Wizards has completely lost touch with how hard it is for the average player to know which cards are legal in which formats. This is only going to make that worse. It also underscores just how much they’ve hamstrung themselves by putting art on their cards that they’re not free to use as they like.
This is a great question, thanks for asking it. I recently went looking for proxies for the first time and found a number of sellers on both Etsy and eBay. The one I settled on has nice art and typo-free text, but the cards seem to be slightly thinner and lighter than a real Magic card. I don’t know yet whether I’ll be able to tell the difference once they’re sleeved up.
I didn’t know about the resources others have suggested here and will definitely check them out for next time.