I'll never understand this sentiment. You don't have to have alerts from slack outside of business hours. Or respond in general. If I responded or looked at my messages every time I got one, I'd never get work done... so I simply ignore them until I am taking a break or otherwise at a good stopping point. It's not that hard.
Oh hey, I am relevant for once. I moved to another city for university a while ago, but kept the job I had before as a half-time remote position. At first I felt extremely pressured through slack. People didnt know my exact schedule and would also write me on days off, and I felt like I should answer asap, because otherwise people would develop the idea that I slack off because I get to work remote.
Well, after a panic attack I changed my approach and asked my colleagues to write me mails instead or ask me on teams where I would only be online on certain days. Everybody just said sure, and work is finally fun again. I think I wasn't the only one either, more and more people started avoiding slack and only look into it maybe once a week.
At some companies you can get a negative performance review for not being on Slack during working hours. “Needs to be more responsive / better team player.” In other places you might be expected to be online beyond 9-5 too.
It's difficult but I'd avoid places like that. If your team won't allow you to close slack for an hour you have serious communication and planning problems. Anywhere I've worked what I do is message anyone who might need vital information from me then just close slack for an hour, do my work and check back in. When I get pulled up on it I give my explanation about focus, communication etc. If they don't like it then I leave. I'm glad it's a seller's market.
