I don't think participation is the problem. If you think about it, you wouldn't want just anyone to post something on a platform without first engaging in said platform. That can only have a neutral or negative effect. People asking stupid questions or people cursing out users. The act of signup ensures that the would-be poster has to signup first and rationalize their post during that process.

Therefor, the problem must be something else, it is the information gateoff (amongst other things) that makes Discord and similar apps unfavorable for community management and information distribution.

Or you can use Github SSO.