Yes it says in this report; two major donors, whose identity the foundation isn't obliged to provide.
I continue to assume that it's set up in the way many charities or foundations are: the capital (presumably invested by H&M) stays in the bank, and the interest is used to fund the charitable activity. I used to work for a charity who treated it's books like that, and it's fundraising efforts effectively paid for our salaries while the interest from the capital funded the charitable work. As a member of the fundraising team I didn't care for ethics of my efforts effectively paying for me to have a job and nothing more, and I left.
I presume that Archewell is similar in that it isn't designed to fundraise, it's designed to be a ringfenced pot of capital well invested that provides a sustainable source of income for charitable activities, a bit like a pension pot. There's nothing wrong with that in principal, and no evidence that Archewell is fundraising only to pay for staff salaries (or that they are fundraising at all!).
From what I can tell Charity Watch has requested some data that Archewell is not obligated to provide. I can see that Charity Watch say things like Archewell only has 2 directors when it is "widespread best practice in the US" that a charity should have 5-7 or so, but it also goes on to say that by law in their state a charity only has to have one director.