That is already way too much as far as I'm concerned. It's not that it's difficult, it's that it's arbitrary and a form of commanded speech or action. Smallness and easiness isn't an excuse.
If you write a story, there must be a character in it somewhere that reminds kids not to smoke. That's all. It's very easy.
I actually don't mind mandating the market take reasonable actions. The EU mandating USB C was an excellent move that materially improved things.
However I think mandated actions should to the greatest extent possible be minimal, privacy preserving, and have an unambiguous goal that is clearly accomplished. This legislation fails in that regard because it mandates sharing personal information with third parties where it could have instead mandated queries that are strictly local to the device.
Under no circumstances should we be “mandating” how hobbyists write their software. If you want to scope this to commercial OSes, be my guest. That’s not what was done here.
I'm not sure where the line between "hobby" and "professional" lies when it comes to linux distributions. Many of them are nonprofit but not really hobbyist at this point. Debian sure feels like a professional product to me (I daily drive it).
We regulate how a hobbyist constructs and uses a radio. We regulate how a hobbyist constructs a shed in his yard or makes modifications to the electrical wiring in his house.
I think mandating the implementation of strictly device local filtering based on a standardized HTTP header (or in the case of apps an attached metadata field) would be reasonably non-invasive and of benefit to society (similar to mandating USB C).