https://jvns.ca/
Not a tech. company blog. Explains technical concepts clearly and top notch technical posts. Fits 1,2, 3 criteria of what you ask, though not the 4th one.
She also publishes a number of technical topics as ZINES. I bought her "Oh Shit, Git!" zine and learned a ton of useful info, despite having decades in the industry.Zines are a great way to encourage book-allergic coworkers into learning great material.