Alternatives to discord, open source or not:

https://alternativeto.net/software/discord-app/

True, but OP wants to run an impostor/mystery, so i feel i’m not completely out of touch, there.

I know. I played Brindlewood Bay, and we felt that the endings were a little off because of the gameplay rules. That’s why I was wondering about throwing an impostor out there to see what would come of it.

I wonder, in a mystery-shaped storytelling, if starting the adventure by secretely telling a random player “you’re the murderer, you killed that person at this time with this weapon at this place” could help you build the mystery part since it would eventually result in having sometimes contradicting information and fake evidence planted by the culprit