I have ADHD diagnosed. I turned off all slack notifications. In fact, I almost always turn off all notifications. My mind is my domain and I choose when others can inject into it. The reason is, my job isn't some disaster related topic (well it is because it's climate change related but that disaster doesn't happen tomorrow). So that means, if poeple really need me, they can come find me, email me, send me a message on slack, or whatever. And i will reply to it when i get it. Nobody has ever seemed to have a problem with this and everyone seems to respect that I have limits on when I want to do things because I have my own things to do.
On a related note, I noticed that many of the things I had labeled as ADHD related went away after going to therapy and realizing why I do things to please others, over achieve and stay constantly involved and on top of everything, etc. It was very easy to label that as ADHD but in fact, the motivating factors that pushed me to reply to every email immediately, reply to every slack message, like, comment, subscribe everything was related to my personal schemas and modes. Not to discredit ADHD as a contributing factor, but I suddenly found like I had control over things when I began addressing these underlying internal beliefs.