The CO2 comes in returnable metal bottles which get refilled after you return them. There's almost nothing disposable at play. If you buy the recent and more expensive models, you even get glass bottles, so less plastic, too.

Sure. I'm always kinda uncertain why people ask for libre software and then not want it for the same things i like about it. If you want something plug and play and decentralization isn't important to you: Maybe you don't need an alternative and Discord is the right thing for you. Otherwise it's not the software (architecture), you just want to go to an existing instance and let someone else do the self-hosting for you.