As far as I can tell, I've put all the apple-touch-icon-*.png icons in the root public directory. The checker though is vague about what's actually wrong.
faq only states that safari ignores overrides--not what this "mask icon" actually is:
If under the "absent mask", the favicon checker noted the 404 above, I feel like I could make an action item. But for now, I suppose I have to manually research every error message's topics to see what they are expecting.
The mask icon and the touch icon (eg. apple-touch-icon-180x180.png) are two different things.
I feel like there is not mask-icon markup at all in your code, is that correct?
Both of those are probably true. I'm suggesting the checker should be more explicit about what is missing and how it knows it is missing.