If you have ADHD and can't concentrate when people are trying to contact you all the time, you should be that person who is unreachable.
That doesn't mean you can't set expectations to help people figure out how to contact you, or give escalation paths if somebody does need you immediately
Exactly. If you’re constantly available you’ll spend all your time on Slack fielding unrefined queries. “Hey did someone on your team touch X recently, because blah blah blah.” Just turn off notifications and ignore it. If it’s important for you personally, it will eventually end up in your email. Let all the people who (for whatever reasons) want to be constantly available be your low pass filter.
That doesn't mean you can't set expectations to help people figure out how to contact you, or give escalation paths if somebody does need you immediately