Hello there!

First off, good for you for looking out for the privacy of others!

Unfortunately, you can't force privacy onto someone. That has to be a choice the person makes for themself. If you want your teen to live a private life, talk to them about it. Explain the dangers of social media, and don't try to sidestep the issue, just be honest. Avoid trying to "trick" someone into privacy, because that leads to bad outcomes down the road.

Using GrapheneOS is your best bet for a private phone. If you want to maintain some control over the device, have your teen use a secondary profile and restrict which apps can be installed using the owner profile that only you have access to. This also adds the benefit of being able to restrict access to the device (if that's your thing) just by restarting it, since the teen won't be able to unlock it. I'm not here to tell you how to be a parent.

Social media I’m not sure if fediverse stuff is the right path especially for lemmy, since it’s just tech nerd stuff and politics which isn’t interesting really unless they go out of their way to find smaller communities.

I agree with this, and it's currently a downside to less mainstream social media. It will always be tailored to a specific community until it grows or becomes mainstream. If you really want your teen to use only open source apps, Bluesky is a good open source option while still being mainstream.

My parents probably want tracking features so it’ll probably be Find My or a 3rd party app like life360

You can talk with them about alternatives, such as an Airtag or other similar devices, or having no tracking at all. One point you can bring up is that it's quite easy to trick those tracking apps (turning off the device, turning off location, turning on Airplane Mode, using a mock location app, leaving the device at home, etc.) so they aren't very useful. Again, I'm not here to tell you how to parent.

It’s just kinda hard trying to blend being a functional member of society and maintain your mental well being and privacy.

This is why privacy is a choice. It's up to the person how private they want to be, but the most you can do is educate about privacy and raise some alternatives.

In general, it depends on how much control you want to have over the digital life of your teen. The more control you have, the less autonomy the teen has and the more likely it is that the teen will resent the practices you put in place. However, the less control you have, the higher the risk of bad things happening. It's up to you which path to take. Something I learned is that you can never have total control, because people are crafty, but people are also very understanding and can adapt to their environment.

Hope this helps!