Need both index.html and index.php

I’m building a site in WordPress but I need to leave a holding page in place until the site is ready to launch.

By default, browsers give priority to index.html, so that would be the default for https://www.domain.com, and I would also be able to go to https://www.domain.com/index.php to view the WP site.

However, the .htaccess is preventing this by pointing all requests for https://www.domain.com/index.html to https://www.domain.com/index.php, and if I reverse this I can’t get to https://www.domain.com/index.php

Here’s what I’ve tried in the .htaccess…

# Remove these 2 lines when going live
DirectoryIndex index.html

# Uncomment this line when going live
# DirectoryIndex index.cgi index.php

Does anyone know how I can set this so that index.html is the default for https://www.domain.com/, but so I can go to index.php when I need to?