Get Link to Feed On Term or Taxonomy

For terms and taxonomies use get_term_feed_link:

“Returns a link to the feed for all posts in a given term. A specific
feed can be requested or left blank to get the default feed.”

See also get_tag_feed_link and get_category_feed_link.

For post types see get_post_type_archive_feed_link.

These functions are located in in wp-includes/link-template.php.