Custombuild does involve gmake, but will try to install it with dpkg -r or ports if It is lacking. If necessary: Add a tailor made certificate before migrating then delete the certificate after your Universal certificate is Energetic. Did you do step #two? This is actually the most commonly skipped https://mautic-installation11110.blogdon.net/5-essential-elements-for-magento-2-migration-42164332