Help with ReWrite

I think what I need is an exact match only ReWrite...
I am self-hosting, and changing to all https:// instead of http://
It seems to all be working withe the exception of the main page, if is fine if you specify index.html, but without it, locally I get router settings login, that is regardless of if http:// or https:// is used to call it. So basically

https://domain.net/index.html (or http://domain.net/index.html)

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works fine, but

http://domain.net

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does not. Any other index file in a different folder in the server directory has no problem weather index.html is specified or not.

I already have in the file 000-default.conf settings that will replace any url starting with http:// to https:// and it works fine.
So my thought (unless someone has another idea) is somehow check for an exact url match before the change from http:// to https:// looking for either one domain.net or domain.net/ and if that is true, with NOTHING else after it, change it to domain.net/index.html

What I have so far sure does change from http:// to https:// no problem, but no luck at all attempting to add the /index.html ONLY if just domain.net is the given url.

  RewriteEngine On

   RewriteCond %{HTTPS} !=on
   RewriteRule ^/?(.*) https://%{SERVER_NAME}/$1 [R=301,L]

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