This isn't really an answer, but I spent a lot of time trying different voice chat systems out a couple years back, but couldn't get my social group to move off Discord.
So, the real answer is any that you can convince the people you want to talk with to use. However other options include Mattermost, Jitsi, Mumble, Teamspeak, and Nextcloud Talk off the top of my head. I think I remember seeing that rocket.chat has voice now too.
Be prepared to argue with people about how they don’t hear the difference in audio quality between TeamSpeak and Discord.
Take it from me, TeamSpeak wins hands-down.
I always felt like the audio quality is similar enough to not matter - but only when one person is speaking. As soon as you're talking while others talk, there's this weird crosstalk effect that sounds absolutely horrible, and this has been in effect since Discords birth.
Just curious, why extremely low latency? If it's for playing music, you might want to look into things designed specifically for that. Something like Jamulus
Ever sat next to someone using the same discord chat and you hear them next to you with just your ears, then about 500ms later you hear them through discord? It shuts my brain off.
How about jitsi? https://github.com/jitsi/docker-jitsi-meet
I am running it for years, works much better than Facebook Messenger that is for sure 😃 not sure what you mean about the "all the standards"