Other than open source stuff I don't see what would be hard to comply with it. Most people use Windows, Gmail and Android or iPhone. At least half of those already do most of what this law would ask.
It seems hard to comply with because any software repository and app store falls under this law and the EU cannot control who uploads a chat app on one of these. At least people from non-EU countries will continue to develop and upload chat apps with full end-to-end encryption and without age verification. So essentially this proposed legislation seems to make all software repositories and app stores illegal, which makes it hard to enforce and comply with.
My guess is that the EU would impose fines on repositories and app stores if they contain such apps and try some ostensibly silly IP geo-blocking, and people in the EU would continue to download and use these apps.
> At least people from non-EU countries will continue to develop and upload chat apps with full end-to-end encryption and without age verification.
You're making it sound more trivial than it would be in practice. Google and Apple would promptly block access to those apps to EU citizens. Android users could still sideload apps but it would likely kill adoption without a massive cultural shift towards valuing privacy.
