Howdy people! Remember me?
A friend of mine has recently published an ebook on fantasy worldbuilding. Though it's geared towards fantasy fans and writers, I really think it would be a treasure for any GM working on building their own campaign world, or further fleshing out an existing one.
No, I have no financial stake in this. It is well worth the modest cover price. Check it out:
https://www.amazon.com/gp/product/B089GKQYVP
This blog post by Matt also gives a taste of what's in store:
https://www.mdpresley.com/post/worldbuilding-for-fantasy-fans-and-authors