There are 2 repositories under opml-files topic.
Awesome RSS feeds - A curated list of RSS feeds (and OPML files) used in Recommended Feeds and local news sections of Plenary - an RSS reader, article downloader and a podcast player app for android
A PHP-based OPML Parser Class. Extracts the properties of content from OPML files
A Dart package for parsing and building OPML documents
Beautify your OPML by removing all the unnecessary characters.
Minify your OPML by removing all the unnecessary characters.
JFlex example: Convert m3u8 playlists into OPML xml files (for example, MusicBee radio import/export format)