And that's an unwelcome intrusion into my time off.

But hey, I like surfing, and you can't 'reach' a person while they are surfing. ¯\_(ツ)_/¯

I don't put company email or company chat (slack) on my phone.

Would you if it gave you more time flexibility? And could set it to only chats for you, not group?

Not at all. When I leave the office, I want to leave work concerns along with it. My off time is for me, not my employer.