Using www in web addresses is definitely a thing of the past, and if you want everything starting with www to be redirected to non-www you can use the following snippet in your .htaccess file:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^(.*)$ $1.html [NC,L]
RewriteCond %{HTTP_HOST} ^www.domain.com [NC]
RewriteRule ^(.*)$ https://domain.com/$1 [L,R=301]

Should you want to exclude a certain url from being redirected (domain.com/something.html) your .htaccess file should look as follows:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^(.*)$ $1.html [NC,L]
RewriteCond %{REQUEST_URI} !^/something
RewriteCond %{HTTP_HOST} ^www.domain.com [NC]
RewriteRule ^(.*)$ https://domain.com/$1 [L,R=301]