Answer
What if my country is not on any waiver list?
Several publishers operate a discretionary route for authors outside the listed countries, assessed on financial need: Sage, BMJ, Springer Nature, BMC, Elsevier, Cambridge and ACM all describe one. Requests must generally be made at submission. ACM notes that such waivers are rare and that stating an inability to pay is typically not sufficient on its own.
Detail
Alternatives worth checking first
Whether your institution holds a transformative agreement; whether a diamond journal exists in your field; and whether a repository deposit satisfies your funder. Each removes the charge without a discretionary decision.