Install multi-site as subdomain setup. Do not use the sub-sites option. Go to Network Admin/Sites and select the site whose URL you want to change: Change the URL to the new domain. In your wp-config.php use define( ‘COOKIE_DOMAIN’, ” ); to be able to log in in both sites. You don’t need a plugin for … Read more
Network Admin URL is shown to anyone before accessing a blog
Multisite, with virtual root
wordpress multisite permalink structure: mostly subdomains but not all
Change Default WordPress MU Blog
One blog inside another
As mentioned in the question itself, this is a problem a non-solvable due to the internals of WP core. What I did was getting rid of the interfering/colliding process – I simply turned it off (as changing the port wasn’t possible).
turning off multi site mode makes XMLRPC fail : you are not allowed to publish posts on this site”
Users are being redirected to main site when trying to register on subsite of my Multisite network
Hierarchy in multisite