Usage: ./makeipsw.sh path/linkto4kota path/linkto4ipsw
Make sure you download the latest actions build from here: https://github.com/verygenericname/futurerestore/actions
(Example futurerestore command: ./futurerestore --no-baseband --use-pwndfu --skip-blob --sep sep/sep-firmware.j105a.RELEASE.im4p --sep-manifest sep/BuildManifest.plist -t pathtoblob pathtoipsw)
The sep would be from latest version of tvos for the 4K