I've found discord to be a very reasonable alternative to slack and I think their branding as a 'gaming service' is more of an effort to carve out a niche than related to functionality. It actually works pretty well as a generic chat / collaboration tool.

We joked at my last job that it was just a matter of time before the business migrated from Slack to Discord. :)

In fact, Discord became the dev teams unofficial Slack backup whenever Slack went down.

Slack does do syntax highlighting. Enter a code snippet and select the language.