It's basically the only working option I've found for the purpose I need (viewing an RSS feed as a webpage in Firefox), and it does the job, but there are two significant issues I have with it.

The first problem is that when viewing a feed that has a lot of entries, the page will take a *long* time to load - more than a minute in some cases - and will make the rest of the browser unusable until it finishes. And your CPU will be under heavy stress during that loading period. If there were some way to add pagination to the feeds, so that only the most recent 20 or so entries were loaded initially, with a button to load more of them, that would probably fix this issue.

The second problem is probably not fixable. The extension appears to load RSS feeds by creating a URL that is unique to your current Firefox installation and cannot be shared with another one. This means that when you switch to a different computer that also has this extension installed and you sync your Firefox profile from your original computer, none of the bookmarks you have saved for any RSS feeds from your original computer will work on your new one. You'll have to recreate all of them which can take quite a bit of time if you have a lot of feeds saved, as I do. Worse is that because the URLs are new, Firefox will also forget all of the history of which feed entries you have already read/watched/listened to. So expect to end up re-experiencing a lot of those entries accidentally unless you have an extremely adept memory.

Ultimately I'm grateful this extension exists since there appears to be nothing else out there to use anymore.