==== required features ====
  * Ability to export feeds
  * Ability to import feeds
  * Add unlimited number of feeds for free
  * web based

==== opml export ====
  * inoreader - preferences -> "Import, Export, Backup" -> Export -> Download OPML subscriptions file only
  * feedly - https://feedly.com/i/opml -> Download your feedly opml

==== what does not work ====
  * feedspot - no ability to export feeds.