What are your experiences with self-teaching music theory? You don’t have to be a 100% autodidact to answer this question; you probably have had times when you read a book or watched a video to learn some specific idea or technique. Ideally, I’d like to compile some guides for readers who don’t have a teacher.
Personally, I prefer close reading of books and articles, but I know that’s hardly a universal approach.
I read books, basically. Starting with the ABRSM’s Rudiments back in 1970 (having been a self-taught guitarist for 4 years by then), and countless (largely forgotten) books after that, just whenever - and only as far as - curiosity drove me. I had the advantage of school music lessons (age 10-11 only), which meant notation held no fears for me. But when it comes to applying what I learned - composing and improvising - that comes from studying music, both on recordings and from sheet music. I was composing and improvising before ever studying any music theory. Still, now, my theory reading is not for any practical purpose, to help me with my own music. It’s just intellectual curiosity, helping build an overview of history and genre. More pieces in the big picture jigsaw.