I've always liked to make bug reports (called issues this century it seems) the center of gravity for task-oriented organization communication. Unfortunately there isn't an obvious best in class solution available but github is usually not too bad. Or the issue system we dare not name (rhymes with era). Communication about non-task-focused subjects in Slack. No DMs unless for palace intrigue. Don't much care about meetings except for socialization. Nothing gets done in meetings but it's nice to shoot the shit once in a while.
Edit after reading other comments: no team private slack channels. Super annoying.