The aunt, uncle, godparent gift, solved
You love this kid. You are not their parent. You do not always know what they are into this month. Your sister has told you they are "way into dinosaurs" but that was in March, and it is October now, and dinosaurs have been replaced by something you have not been told about yet.
The gift-giving problem for people in your position is not lack of caring. It is lack of daily information. You are pattern-matching from Instagram photos and Christmas dinners. You have limited data on the current obsession.
What people usually do
The clothes gambit. You buy something you think they'll like in the size you think they wear. Half the time the size is wrong. When it's right, they wear it once, and you're not there to see it.
The gift card. It works. It also announces that you gave up trying. Kids do not have an emotional relationship with a gift card. The kid getting a gift card knows the exact number.
The Amazon list. You ask their parent for a list, and now you're one more thing on your sister's to-do list, and the item you buy is something the kid already picked out and knows about, and there is no surprise in it for anyone.
A different move
Ask their parent, one time, one sentence: "What is [kid] into right now?" You will get back something like "Octopi and any book about magic wizards" or "She's still on Trolls, believe it or not, and also frogs". That is enough.
Then come here.
You spend three minutes filling out a form about the kid. Their name, their age, what they're into (the octopi, the wizards, the frogs). You pick a setting and a mood you think fits them. You sign it however you'd sign a card. You pay nine dollars.
A minute or two later, a link comes back. You text it to whoever is going to hand a phone to the kid on the day.
The link is a small game made just for that kid. Their name is in it. The octopi are in it. It's obvious it wasn't picked off a shelf. Obvious in the specific way that matters, which is that a kid who plays it knows an adult in their life put attention on them.
For the godparent specifically
Godparent gifts get held to a slightly higher bar because of the promise. This kind of thing works well as the third or fifth or fifteenth gift of a lifelong stack because it's cheap enough to give often, specific enough to remember, and doesn't add to anyone's clutter.