Make conversations public by default. If you use Slack, make team channels, project channels, announcement channels etc. all public. Discourage 1:1 and private communication unless really necessary, especially for engineering topics. This single change will have an immense impact on overall company culture.
I'm at a company now where we are trying to do this but the CIO/CEO keep weighing in on EVERY conversation where they disagree with the approaach. The whole reason we are having the open conversation is for ideation and good communication but when a high level person comes along and says "well thats not the way I would do it" everyone decides to go back to 1:1s, direct messaging, and calls so as not to document anything publicly in feat of being called out by the higher ups.
I was going to say the same thing. Had this setup at my last job and the CEO would chime in with irrelevant, outdated, not feasible, or already considered ideas. We'd then have to spend time communicating and explaining the shit we had already been talking about for the last month or whatever. It was incredibly frustrating because it gave a public impression that our team was either incompetent or combative. It was gross.