Entry page for a wordpress multisite

You have at least three options:

  1. use a Child Theme on mysite.com, in which you replace index.php with whatever you want
  2. Use a different Theme entirely on mysite.com – could be a landing-page Theme or whatever.
  3. Use your current Theme on mysite.com, but set it to display a static page as front page, put your subsite links in the page content of the page displayed as the site front page, and remove all other content

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