If you do not trust your own devops, why are you trusting someone elses devops?

It's just due diligence. Think of what you have access to if you have "god mode" on corporate chat: HR, the CFO's DMs, private messages between other coworkers, and so on. Most won't fall for this temptation, but even those with strong anti-spying morals can be weakened by circumstances. Best to remove the temptation by design.

Because someone else's devops can't use it against you institutionally. Nor is going to insist on having an opinion on things that they're unaffected by.

This isn't a slam at devops, it's about the need for institutional information hiding; not everyone needs to know about and weigh in on every decision being made.

We structure our company similarly. With effort DevOps is god on everything except HR, Sales, Finance, Chat, and C-level management which are operated with 3rd party services controlled by the individual departments and "owned/managed" by the C-suite.

Low maturity risk management functions.

Slack won’t protect you from this as it’s possible for admins to export even private DMs.

https://www.nbcnews.com/better/business/slack-updates-privac...

Only Slack Workspace Owners can export, not Slack Admins.

You also have to be on the ‘Plus’ plan, otherwise it is a roach motel.

Devops should have nothing to do with your chat server. It should be your IT department, just as with the email server.

DevOps at a lot of small companies also manage the internal IT stack and sometimes even take on most of the IT duties. Once you get larger you start having "IT" as something separate from DevOps but with the actual infrastructure managed by operations. Once you're really big the teams are truly separate and IT owns their own infra.