Among other common reader functionalities, it also supports not just OPML import/export, but OPML subscription as well.
In addition to a number of pre-configured share buttons, you can add custom share buttons. You can enter a custom URL for the share button and include variables for the page being shared: [URL], [TITLE], [TITLE_NOENC], [CONTENT], and [SOURCE]. You can also choose whether to use a GET request or a POST request.
For example, you could use:
https://quill.p3k.io/new?reply=[URL]to reply to the URL using Quill.
https://www.example.com/wp-admin/post-new.php?kindurl=[URL]&kind=replyto reply to the URL using Post Kinds Plugin for WordPress. (One could also replace 'reply' with any other kind names (bookmark, like, listen, read, etc.) to create other types.)