I am trying to remove .html from url which aren't posted using WordPress using below code :-

RewriteCond %{THE_REQUEST} /([^.]+)\.html [NC]
RewriteRule ^ /%1 [NC,L,R]
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^ %{REQUEST_URI}.html [NC,L]

And the htaccess provided by WordPress is :-

RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

The html file I am trying to remove html extension from is not a post but external file uploaded in c panel, any help would be greatly helpful thanks! embers of divinity