Once on medium.com, press the add-on icon and observe that for each story, the "X min read" field becomes gray (refer to the screenshot). If you press on this field, the story will get hidden. Next time you visit medium.com and press the addon icon, all such stories will be removed.
Additional functionality is to keep loading stories until there are around 30 in the feed.

Install

• License: Mozilla Public License 2.0
• Weekly downloads: 0
• Average daily users: 1
• Rating: 0/5 of 0 ratings
• Created: 2019-07-19 07:53:34
• Last updated: 2019-07-22 06:10:11
• Homepage:
• Support site and email
• Orig: https://addons.mozilla.org/en-US/firefox/addon/medium-story-removal/
• API: {02a4ef3d-4910-472c-b443-0c7083661ff3}