How to compose rule to exclude .html in RewriteRule?

Question

htaccess

RewriteRule ^(.*)\.html$ 404.php [R=404]
how to do negation, i.e. where to add!
so that the rule works for /123.htm, /123, ..
well, of course, so that for / does not work
, you can test here htaccess.mwl.be

Answer 1

The first time I see a question with an answer, well, just put it!
cond is if and if and if then
RewriteCond
RewriteCond
RewriteCond
then

RewriteCond %{REQUEST_URI} !index.\html$
RewriteRule ^(.*)\.html$ 404.php [R=404]