Generate HTTPS Urls in multisite

Instead of get_option, use home_url which will determine …

the appropriate protocol, “https” if is_ssl() and “http” otherwise. If
the $scheme argument is “http” or “https” the is_ssl() check is
overridden.

In fact, network_home_url would be more appropriate since you are talking about Multisite.

Those should return the same value that you are trying the access in your code– the home option key– but with the appropriate protocol.

This may not be the URL you want though. You may want site_url or the multisite equivalent, network_site_url.