Upstream: https://github.com/JGRennison/OpenTTD-patches/releases
flatpak-builder build --force-clean org.openttd.OpenTTD.jgrpp.yaml
Push to local repo
flatpak-builder --repo=/var/www/html/repo --force-clean build org.openttd.OpenTTD.jgrpp.yaml