As has been mentioned, blending/pureeing vegs is also supposed to make the nutrients more accessible and probably easier to digest as well, because it “chews” the food better than you can.
I buy Weber AllGreens Superfood, just because it’s a good price at my CostCo. I had trouble finding the nutrition info, but apparently it’s 5 carbs per serving. There is at least one brand of greens with keto in the name, with 1 carb or less; you can probably find it if you do an Internet search for keto greens.
The kind I buy also has fruity stuff like blueberry and acai, as well as stevia and a small amount of maltodextrin and saccharose (another name for ordinary sugar). Ew. I hate the fruity sweet flavor and have to mix it with a bit of V8 and lots of ginger to make it palatable. Just sayin. The “keto” brand has fruit and berries too.
Or you can make your own mix of spirulina and chlorella. These two ingredients provide different nutrients, so by combining the two you might cover most of the bases. They taste fishy but not too bad.