Oh no, please, not more spam. I don't need notifications, for anything.
I will look at communities when I have time to read and write replies, not when the buzzing rectangle in my pocket tells me to.
The only notifications I have on is for phone calls, even that not all the time.
Also, those notifications are what makes traditional "social" media addictive (among other things), we should not do that, for ethical reasons. We know that it has mental health effects and causes other issues.
The time of people matters. Having people get info unless they opt out is a dark pattern.
I wonder how many health effects this would cause for many people.