> When everyone is working from home it's not like I could just call someone and chat to them because I don't know if they're busy or not

I don't really see what the issue is. In my company if we want to chat we simply ask on Slack "can we have a call?", and the other person either says 'ok' or 'call me later'. Most conversations happen over async chat, which is great if you are waiting for something to compile (Scala...).

How do you do it in an office setting? Would you go over to a person wearing headphones and starting telling them about your weekend?