I've stopped using swayimg, but I feel obliged to leave a comment, since I last touched the template. EDIT @Duncaen I was in the middle of typing this, when the PR got merged. In short, upstream switched to lua configuration, and installing config files would have to be adapted, please see: https://raw.githubusercontent.com/artemsen/swayimg/refs/heads/master/CONFIG.md

EDIT2: Probably something along these lines in post_install():

vmkdir etc/xdg/swayimg
cp extra/example.lua ${DESTDIR}/etc/xdg/swayimg/init.lua