There is at least one workaround, if you don’t mind being a bit flexible.

GitHub lets users add multiple email addresses to their accounts and assign them as notification recipients. I’ve added a Kill-the-Newsletter (not affiliated) email to my account, and then use custom routing to route all emails for orgs I’m a part of to my email address - and everything else to Kill-the-Newsletter.

With this setup, all notifications related to orgs I specify come to my primary email address, anything else by default hits the RSS feed from Kill-the-Newsletter and keeps my inbox from getting slammed when a particular issue/etc. has a ton of activity.

I’m working on them - hopefully next!