Is it possible to list my products on Walmart without a UPC or EAN number?

Yes, but you need exemption from them However, you must have UPC or EAN number to sell at Walmart or even any other Marketplace. Barcodes are the unique identifier for marketplace catalogue to get the same item pull up easily our of their big databases.

Now question is how you can get them easily. Brand should have mainly from GS1 but that is expensive but you could have even from other multiple website if you purpose is to list and sell your product online.

We recommend you to buy from https://codesforamazon.com/product-category/barcodes/ean-numbers/