Better version of the #HINARI list (2018):
https://web.archive.org/web/20180112190448/https://www.who.int/hinari/eligibility/en
72 group A (poorest); 47 group B (not so poor). That covers about half the UN member states.
I seem to remember other journals that give low or zero APC for poor countries but give no partial waivers for middle-income countries. Something like another glass ceiling against researchers in middle-income countries.