I'm always connected to IRC #python-dev (Freenode) for 10 years, a few other core devs use it time to time. Come to say hello ;-)
The bugs.python.org and buildbot notifications are useful to me and I don't feel annoyed by them. But GitHub review are hard to use: only the user name and the PR number are given: PR title and comment content are not provided, you have to click on each link to know more. Moreover, when a user leaves 10 comments, there are 10 IRC notifications!
11:17 < Not-4ecb> [cpython] shihai1991 reviewed pull request #26103 commit - https://git.io/JsOQn
I almost never go to Zulipchat. I was there one month ago, 6 months since my previous visit. There were few messages.
Mailing lists, discuss.python.org, IRC, Zulipchat, Twitter, private messages, etc. Well, I have enough communication channels to talk with other core devs ;-) https://pythondev.readthedocs.io/communication.html