Thanks for the answer but It does not work!!! I can get to the select file part, then it just does nothing... I feel kinda dumb upgrading first to Mac OS and then not being able to install iOS hahahaGo into finder you’ll see your phone there. Then restore like you did in iTunes using the ipsw file.
Edit.. I tried with the PKG only on Catalina, didn't help (and yeah, I rebooted