OK, the screenshot helped. You need to replace the font inside the Strategies.pdx with the new file. Not in decks. The font replacement could be classed as unsupported modding.
Viewing post in Strategies for Playdate comments
For unknown reasons I had made it so that custom fonts only worked in Deck mode (not Quiz or Interactive Fiction) but I’ve uploaded version 1.2.4 that allows custom fonts to work in all modes.
https://gingerbeardman.itch.io/strategies/devlog/903447/changelog-124