.htm on PAGES
Appends .htm to the URL of PAGES when using permalinks
མཐུད་སྣེ་འགྲེལ་བྱང་།: htm
Custom Page Extensions
Allows you to add a custom extension to your page URLs.…
WP Page Extension
Converting an old HTML, PHP, or ASP site to WordPress? …
.htm and underscores on PAGES
Appends .htm to the URL of PAGES when using permalinks …