The licence question is smaller than it looks
An e-commerce licence is available on the mainland and in most free zones, and for a business selling physical goods to UAE customers the mainland is often simpler because it avoids the question of who imports and who distributes.
Where founders lose time is the activity list. Your licence names what you are allowed to trade in, and adding a category later is an amendment with a fee. Write the list wider than your first product, within reason. It costs almost nothing at setup and saves a trip later.