I'm curious about some of the suggestions people might have.
For art and design I subscribe to newsletters from Dezeen, Hyperallergic, and Artnet, among others, like local museums. Dezeen articles I usually like to read; the other two I don't read the articles of as often but when they do have things I'm interested in, I'm really interested in them. Smithsonian News is also good, not just for art but history as well. I regularly read that.
I should probably look into similar things from foreign museums or museums out of state.
Strangely enough, I also really like Google's Art and Culture app? I probably don't use it as much as I should, or as much as I like it. I kind of forget about it unfortunately. Sometimes it can be kind of superficial but it has a lot of content and alerts me to things I wouldn't otherwise see, and the articles can be just the right balance of length and depth.
I've found that newsletters are helpful just in terms of being reminded of blogs. I probably get too much email but it also pushes me to unsubscribe from things I don't like. Most of the noise is from retail business too and not blogs or nonprofits.
For books I should probably keep track of better but I like NY RoB, Los Angeles RoB, Paris Book Review off the top of my head. Guardian Books is a newspaper but one I track.
I also have found it really useful to pay attention to publishers and presses you like and subscribe to updates from them. They're not blogs per se but you can often get newsletters with new publications. In addition to The New York Review of Books, for instance, there's also the New York Review Books, which sends out newsletters about books they're releasing that I often find interesting.