I had high hopes for this extension but the interface feels really clunky and unintuitive. I'm providing this feedback hoping that at least some of these points can be improved in future updates.
- I keep expecting to be able to right click an entry in the article list to display a context menu to mark it as unread/read, mark this and all previous articles as read/unread, star, etc., but this opens it in a new tab instead and I see no way to change that functionality.
- For some reason sometimes when trying to switch between feeds by clicking on one the first click only highlights the feed and a second click is necessary to actually switch to it, this is intermittent though. (This may have something to do with having two Feedbro tabs open and adding a new feed on one of them)
- Selecting "Show only unread articles" doesn't refresh the list so it initially seems like it's not doing anything.
- When changing the "Feed entry content" it's not obvious that only new articles will be effected so again, this initially appears to do nothing.
- When using the Dark theme, if using the full article view and the page includes hard-coded dark fonts the text is almost invisible.
- The Feedback link for the Firefox extension for some reason brings me to the Chrome Web Store instead of the Firefox Add-ons page.
- The tooltip for marking an article as read reads "Mark this entry read/unread - Shortcut: m" but this seems to only work intermittently, if it stops working refreshing the page allows it to work again.
- It's great that this supports keyboard shortcuts, but for some reason arrow keys aren't used. I would expect to be able to move through the list of articles with arrow keys.

It's obviously not all negative though, I was surprised that this RSS reader supports custom rules and I love how much control this gives me to change what is displayed. The functionality to search for RSS feeds in the current page is simple but also very useful.