This extension has a popup that will give you the option to select from feeds on a page natively, or with RSS-bridge configured to your liking. It optionally integrates with tt-rss to include a 'subscribe' link.

Supports twitter, instagram, and youtube RSS-Bridge.

This code is inspired and cloned somewhat from https://github.com/idealclover/Easy-to-RSS/. Icons are sourced from this repository as well.