You can use party voice chat on your phone (Xbox app) while playing the game on your Linux PC.

Most distros can even connect to your phone via Bluetooth and you can mix the audio+microphone into your PC headset.

I’ve done this before in KDE Plasma and it worked seamlessly.

Looks promising!

These are the candidates? They look like clones.

A Head in the Polls

You’re out.

Also, if you’re making something similar to Smash Bros, remember to keep the movesets/combos relatively simple. Too many complicated combos will make it harder to pick up and will be harder to balance.

Potential names:

• FOSS Fighters
• Open Tournament
• Libre Brawl (Or some combination of these)

I think is best to start with common archetypes (think DnD classes) and make movesets that feel right within those stereotypes. That should make a good starting point and you can tweak from there.