My experience someone who work for Red Hat, I had only (engineering) good relationship with the IBM people, i never heard anything about lay off or projects that needs to be killed or other devil things IBM people may do because of IBM , they are rather nice most of them actually.....

Where did you work in RHT? In the openshift org everyone is on slack, i haven't touched to my IRC client for a long time (for work stuff at least)

The older engineering orgs are on IRC, partially because many of the upstream communities were on IRC. It's slowly changing for the same reason (IRC falling out of favor in the broader community).

There's a mix of IRC, Slack, RocketChat, and GChat.