COPPA (the child privacy law) requires you to add code to your game in order to be compliant. It includes adding a tag to all of your ad requests that marks the ad with child directed treatment, which disables interest based advertising and remarketing, both things that collect data (so in other words it turns off data collecting for apps that are played by children).
edit: I had originally written a wall of text about GDPR as well (the EU privacy law), but after reading about it more I believe that you can be compliant without utilizing any tools from Google that require coding knowledge.
But either way, the problem is that gdevelop has the ability to put admob ads in without code, but no ability to be legally compliant with COPPA without code, which means you can’t be using the ads if the game is for kids.
(btw, it’s much more clear now since the last update in gdevelop that you need to be using test ad units to test ads, which I thought was really awesome and really appreciate seeing 