The Orbital Index, for weekly updates about the space industry: https://orbitalindex.com/
Bitcoin Optech, for weekly Bitcoin news: https://bitcoinops.org/
Lil'log, for well-written content on topics in AI: https://lilianweng.github.io/lil-log/
The Gradient, for the same reason: https://thegradient.pub/
Slate star codex, no explanation needed: https://slatestarcodex.com/
I also subscribe to releases for Python, Julia, Rust, Matrix, Jami, LBRY, and a few others.
And a shameless plug for my own blog: https://jarbus.net
I use newsboat as my RSS reader, lovely way to check the day's feed from the terminal.
Here are the feeds I subscribed: https://feeds.pub/timqian