Giver of skulls
Oracle has a generous free server offering. You will need to trust Oracle not to turn off your server because a business customer needs it, though. Availability of their good free tier also fluctuates and you need to figure out their weird IP/firewall/security config.
You need a domain name to effectively federate, too. There are free options available for those too, but they’re not very reliable.
We pretty much had this when the first reliable Mastodon<->Bluesky bridge came online. The Fediverse side protested and made the entire system opt-in, making it practically unusable because people that don’t have a favourite Linux distro don’t know what a fedi is and why they should bridge to it.
When this goes live, I expect people to treat it the same as every other sizeable social media joining the Fediverse, with outrange and block lists.
I’m not a parent (and I’m glad I don’t have to think about this problem myself). However, I’ve worked at a company that specialised in filtering internet services with many parents using it to protect their kids. I’ve also talked to plenty of people whose parents used to deny them whatever app the kids were on at the time. I can tell you that many kids will install apps and create accounts eventually, whether you permit them or not. I’ve seen the ingenious workarounds kids will come up with (using the browser app built into Windows Help to get around parental controls, combining web proxies and VPNs into an unholy homebrew Tor, or just using a burner phone outside the house), and while I appreciate the hacker culture that can develop around hiding apps from your parents, I don’t think it’ll be good for the relationship between you and your kids if you’re too strict about this stuff.
Snapchat is popular because other kids are on there. It’s mostly a stupid looking chat app. Every other chat app out there has cloned its most important features. Your kids won’t be missing out on anything on there, except for the network of friends and social activities that are there. That means you won’t find a Fediverse app like that, because most teenagers aren’t on the Fediverse. The other kids aren’t going to replace Snapchat with an app just to chat with your kids, especially not if it sends a copy of their conversations to their parents. Best case scenario, they install the app and share most of the stuff your kids are missing out on on the special server you set up so your kids don’t miss too much.
As for the point your daughter made, notifications can be silenced. If your kids are worried about phone addiction or getting interrupted by notifications, help them with whatever digital wellness tools their devices come with. Every major OS, desktop and mobile, now comes with tools to limit notifications during focus time, bed time, and the ability to silence notifications for certain chats or events. I find it hard to believe that Snapchat would solve that problem and feel like it’s more likely she’s using an unrelated valid concern to help her case for your permission to use Snapchat.
I don’t know how old your daughters are and what guidance they need, but if they’re creating PowerPoints to get their desires across (bravo), I think they’d be better served with guidance than with alternatives. Instead of rejecting them, consider permitting apps like Snapchat under certain conditions (time limits, no publicly posting pictures, no strangers, etc.). It’s probably also best to make the rules are clear and consistent (which means not taking away Snapchat time as punishment for arbitrary things), because that kind of stuff can cause trust issues that will still have them go behind your back. For this to work, they need to trust that you will honour the “deal”. I’m not saying you should let 12 year olds go ham on social media, but letting 16 year olds on Snapchat an hour a day isn’t going to kill them.
The biggest risk with these things is that kids will find a way to install these apps without you noticing, something bad happens (their online friend turns out to be a grown man, a classmate starts sending weird messages), and they’re afraid of talking to you about it because they might get in trouble for having a banned app on their phone.
Kids shouldn’t even be on social media, but at least the corporate ones are covering their ass against lawsuits well enough that they try to moderate content.
The Fediverse is not a place for kids. Servers catering especially towards kids are DEFINITELY not for kids, because that’s exactly the kind of server I would build if I were a pedo.
The legal requirements for hosting content for kids are a massive headache that you definitely don’t want to take on as a volunteer. The Fediverse can’t even comply with the GDPR, let alone COPPA and its many international alternatives that actually see enforcement.
Of course I was a kid on the internet too and very few websites care about lying about your age, but if you do that and see the occasional dick, fetish porn or gore, you’ve only got yourself to blame. Plus, the Fediverse is full of misinformation, lies, and propaganda, from every side of the spectrum. Moderators can only do so much, and some moderators straight-up post misinformation and propaganda themselves. Best not to expose kids to any it that shit until their brains have developed a bit more.