Fabulous! This is a much appreciated and good replacement for the ditched rss-feed function on firefox 64.
I'm pleased with the slender layout in a sidebar.
May I add some suggestions:
- It would be great if we could rename the rss-feed entry (comes sometimes generic...)
- It would be a luxury if we could move the entries as we wish up and down
Thank you very much and I do wish you will continue your invaluable work. Looking forward to any developments. Cheers!

https://www.bbc.com/news - no feeds detected, the addon doesn't find rss feeds on some webpages having them. You have to add those feeds manually. But Simple Rss plugin is the best of all existing for Firefox 64+. Author of the addon, please exchange windows positions in sidebar: move rss list to the bottom and rss content to the top and make the windows resizable.

For me, the worst thing is that you can not normally save the source of a website so that you can download information and notify the user about new messages from any internet service, and I would like this additive to be improved in this respect :-( I would highly ask that this explosion be definitely improved to make it possible to use it comfortably and intuitively, and to be able to add different addresses of websites so that this add-on can download and notify new information of the user using this add-on :-(

First of all, thank you for picking up the baton on a Sage replacement!

A little feedback:
The addon doesn't handle feeds in sub folders like Sage used to. I have hundreds of feeds saved and having them all in one giant list is not an option.
In Sage, clicking the feed title would show the contents of the feed that was displayed using a user editable CSS stylesheet. This was really useful for setting your own layout, text sizes etc.

Looking forward to seeing this addon improve.

Great !
However I would have two remarks. The extension doesn't seem to understand the native firefox format used for the feeds, no big deal though but the experience would be smoother I think. A more annoying point is that there is no indication if the link has been visited or not (make it bold for example ?), it should be feasible using firefox history.
Ah, and adding buttons to mark all entries as read or unread would be a nice addition (I come from sage too, does it show ?).

Anyway, such a simple extension that does not try to implement its own history different from the firefox one is really good news, thank you !

les flux rss indiquent "Loading" et rien n'apparait

So nice - so simple.
As to the points the last commenter made It's very much subjective (no disrespect).
Install the add-on, add the bookmark of feed page to simple feeds folder and that's it. The feed headlines are updated when the feed page is, and past headlines are gone. Didn't read the feeds before the page was updated - miss that day(s). A simple scroll through a list and one recognises past headlines.
If you have to know all and every feed headline, this is not for you, but if you are someone who feels they are drowning in information, with hundreds of headlines demanding your attention, you may well like this.