From [this Reddit post](https://www.reddit.com/r/InoReader/comments/8jt2pa/how_do_i_put_all_my_youtube_subscriptions_on/).

1. [Use this YouTube link to download all of your subscriptions as an OPML file](https://www.youtube.com/subscription_manager?action_takeout=1)
2. In Inoreader: Cog -> Preferences -> Import/Export, and import the OPML file