Download the source code and ISOs of distros without age gating and put them on durable media. Tell your friends about the issue and its implications (legislating how an OS works is a huge deal, is likely unconstitutional, and opens up the door to all kinds of future abusive laws). Find like minded people so if the worst happens you will have mutual support and can work together on circumvention of any future restrictions. Work on your C skills.

That is the most serious thing you can do, and the most effective.

Do you know how democracy works? There are these people called representatives. They are hired by you. They pass laws. They only get to continue having a job if people like you vote for them. When you tell them "I don't like the law you are passing", they are hearing "the people who hire me are angry with me". The more people that are angry at what they're doing, the more their job is at risk.

They do what the lobbyists say because somebody else is doing the work, and they get paid (by the lobbyist). But they won't have a job to get paid for if the voters don't vote for them again. So your entire defense against tyranny and bad laws is you speaking out. If you never talk to your reps (or vote), you're telling them you don't care what kind of government it is, and they really will do whatever they want.

You have to tell them how you feel, along with all the rest of us. That's the only power we have.

In addition to that, tell everyone you know. Your friends, family, coworkers, the dude running the local gas station. Explain to them why government-mandated surveillance of everything they do on a computer is a bad idea. Ask them to talk to their reps.

Do your homework, vote, and help inform other people so they vote too.