Fictionwise has some MultiFormat MZB, sold without geo-restrictions or DRM, directly from her estate.
Here's a
collection of her Darkover short stories, written from points all along her career, and I recommend them as the best introduction to Darkover and her work in general.
You can also find a couple of her oldest Darkover novels (some of them are the out-of-copyright ones, but I think they might have new introductions by the person who handles her estate) which are admittedly not the better ones (the ones written mid-career are; best to save the ones from before the mid-60s and after the mid-80s for later reading), along with a bunch of her other rights-reverted books and some of the short stories written by the contributors to her shared-world Darkover anthologies she used to edit until that unfortunate incident after which she officially shut down all submissions.
There's currently a 50% off discount coupon for Fictionwise in the Deals forum, and if you miss that, then they seem to have a big sale every Xmas/New Year's.