I’m wrote a book about why all knowledge of the truth is fundamentally uncertain. Give it a read!
I’ve also written a lot about AI safety, personal development, and Buddhism, among other things. Most of that’s here on LessWrong, but there’s also some on my blog, Uncertain Updates.
Sure. I’ll give some links shortly since I don’t want to recapitulate too much of what I’ve already written, but basically the Enneagram tries to predict your behavior based on how you orient towards being. That’s kinda vague, but the idea is that some people’s deepest desire is to love or to understand or to accomplish or something else, and when they are inevitably prevented by the world from fully doing that, they develop coping strategies that ossify as habituated behaviors, and those habituated behavior are what constitutes personality as normally understood. This is different in that most theories don’t aim to theorize a mechanism by which personality arises; they merely seek to catalog the existence of different personalities.
I wrote a few posts about the Enneagram. You can find them both here on LessWrong or grouped together here on my blog: https://www.uncertainupdates.com/t/enneagram
What I’d actually recommend you read, though, is @Valentine’s series on the Enneagram. The last post in the series is here, and it has links to the earlier posts so you can read the whole thing.