Fluxer is still very much in alpha/beta, and documentation for self-hosting is yet to be written.

If you'd like to host something more mature that offers 90% of the functionality of Discord, I'd recommend hosting an XMPP server, which would enable you to also host a Movim instance on top of it. You can ask for help as a beginner in !selfhosted@lemmy.world to get started :)

You could also use Movim without hosting it yourself, since it's already federated like Lemmy/Piefed are.