First link has a typo (an errant á), should be: https://krita.org/en/item/funding-kritas-development/ .. however it's even older (from 2016)

Their windows store buy page[0] (also from 2017) suggests they'd prefer you donate than buy.. so it's probably not a viable model.

[0]: https://krita.org/en/item/krita-available-from-the-windows-s...

they don't give away a cut to steam if you donate, but then you lose the automatic updates, but sometimes I think steam is slightly behind the on releases anyways...

Just drop the á https://krita.org/en/item/funding-kritas-development/

Looks like $6000 from steam, or 10%, in ~2016