3/4 of the team I am on work from home, 2 of us full time, We have weekly scheduled meetings with no agenda other than to catch up and this is where ideas can come up, We haven't all been in an office together since before the lockdown yet we continue to thrive. I also have most of each Friday blocked out to work with one of the team on whatever he happens to be working on that day. We just jump in a meeting and do stuff. And like you we are all open to just spontaneous chats at any time either by text or call. It works perfectly well.

I guess you also have those chats where you pull other people in during the conversation, Oh, Suchandsuch will have input, send them an invite to this meeting etc :)

I love it, I get peace and quite when needed to code, and all the interaction I need to make the job work.