Oh I fully agree. This wasn't to say we don't need a federated solution. It's simply that i did not find any FOSS solution which was readily available.
I tried revolt in the past, but post rebrand their website doesn't even mention voice anymore. It might be there? The article somewhat confirms part of what I said ( not really many FOSS alternatives which are mature/fill the use-case, let alone distributed ).
Matrix is mature enough but I've heard getting voice to work is not that straightforward. It's also not as simple as registering and building your space. You can self host it, but then you're responsible for hosting/security/patching/upgrades/... . Which is outside of a large audience their circle of interest. You could rent a matrix server, but that a quick search gives me servers around 50€/month. That is a pretty steep price just for some voice chat with friends. If there's a proprietary free version people will always just do that. The only ones who don't are people who do it out of principle.
People will take the path of least resistance, and as it stands I feel proprietary software currently is ahead ( simplicity, features, maturity, ... ). The downsides obviously being the fact your data is being sold off. I'd not now then when they've reached critical mass and the VC are looking to squeeze to get their investment back with extras.
I mentioned big tech, but I should have said proprietary as it's not necessarily a big tech alternative.
But yes, I would love to have a distributed FOSS discord-like software I can use with my friends.
But as it stands I can't even get people to move away from WhatsApp for signal despite the nightmare that is meta. Let alone convincing people to move to something less polished when their friends are using <other tool that is polished, but proprietary>.
Let us hope comes up while there is still momentum.

