What works for me for a long time is total separation of work vs private online life. On my work laptop, no social media, private email etc is set up, whereas on my private laptop there is no access to any work related stuff. Also, no work email/chat on my phone.

So no private notifications during working hours and if I really have to focus, I just turn off email/chat temporarily.

On the other hand, after I finish work, zero work related notifications can reach me.