Corporate Slack instances are probably not a great place to discuss such things. One could in a pinch fire up one of the ssh chat daemons [1] on an EC2 assuming that most of the employees are familiar with using SSH. There is a demo documented in that git repo. People can ssh under a pseudonym rather than using a real name. The daemon uses private keys to track identity so make a new SSH key specific to that server. Not my repo but the maintainer is here on HN.

    # append to ~/.ssh/config
    # ssh-keygen -q -t rsa -b 2048 -N "" -C "chat" -f ~/.ssh/ssh-chat
    Host chat
        Hostname some-ec2-ip
        Port 22
        User some-username
        IdentityFile ~/.ssh/ssh-chat
        # Go's ssh lib is old
        HostkeyAlgorithms +ssh-rsa
        PubkeyAcceptedKeyTypes +ssh-rsa

Another quick, lightweight and simple option is uMurmur but it would require people installing Mumble on their laptop or Mumla on their phone so that's extra friction.

[1] - https://github.com/quackduck/devzat