

There’s a reason it only supports Pixel phones: none of the other manufacturers produce phones that are suitable for it. All the other ones either don’t let you unlock the bootloader, won’t let you relock it with your own keys, or disables other security featurea. Meaning anyone can just flash whatever code they want to the phone and completely nullify the security model.
For a bit, OnePlus did support this but they quietly removed that feature with the Android 12 bootloader update, and otherwise cut you off from the TEE anyway so the OS can’t even verify the boot chain.
The GrapheneOS team said they would happily support other devices if any met their criterias for support. None do. Pixels are the only phone where you can properly flash a custom OS on, and relock the bootloader and disable OEM unlocking like it’s the official OS with all the security features functional.
No, I would simply give them a box of condoms or whatever.
If they’re gonna do it, they’re gonna do it, and as a parent, you’re way better off with your kids comfortable not hiding it because if there’s complications you can intervene quickly. If the condom broke, you want the kid to come to you so you can get plan B and not have to deal with an abortion a couple weeks or even months later. It’s also way better they get caught doing it at home vs in a car and now be on the sex offender registry.
What you’re describing is abstinance and is common in religious families, and well know for being ineffective. Plus as you’ve described, it completely falls apart when bisexuality is involved, and it makes even less sense if it’s physically impossible to even get pregnant.
The same extends to alcohol, drugs, porn, whatever evil vice people are worried. If your kid’s gonna do drugs, you want them to feel comfortable calling you if they have a bad trip, and also feel comfortable giving you the drugs so you can get them to the hospital and they can quickly identify what you’re on and give the necessary medications.
They’re gonna learn about all that eventually, better they learn it from you. Punishment and “you’ll understand when you’re grown up” doesn’t work. If they’re old enough to ask, they’re old enough for the answers too.