Answer
Do APC waivers cover books, chapters or conference papers?
Not usually. Country-based waivers are written for journal article processing charges. Book processing charges and chapter charges are separate schemes with separate terms. Conference papers depend on the organiser: ACM, for instance, extends its geographic waivers to sponsored conference articles as those move to full open access.
Detail
Check the scope line
Most policy pages state which content types they cover. Where a page is silent, the safe assumption is journal articles only.