I second https://www.brainpickings.org/ and also would like to add http://nextdraft.com/ (though it is more "general news") - other than that I can't help, because I actually prefer to use rss-feeds over Newsletters.

Some RSS-Feeds I follow and which might be of interest: http://kernelmag.dailydot.com/ - http://www.rand.org/blog.html - https://blog.codinghorror.com/ - https://bsdmag.org/

(PS: You can also get rss-updates about new entries in Youtube-Playlists (google it) and if you use Twitter and follow some interesting people, that might also be a good way to stay up to date)