What I use on desktop is Feedbro.

Unfortunately this is only for the Browser help forum any addons or extra will have to be found from the site your asking in question or contact their support.

WestEnd said

Unfortunately this is only for the Browser help forum any addons or extra will have to be found from the site your asking in question or contact their support.

People are welcome to ask for help with Extensions and Firefox here as asking the dev of said extension is not the only option.

OscarRomero said

Why can't I find an add-on for RSS? All say Not Supported On This Platform. I've tried 5 or 6 add ons.

You posted this in desktop Firefox section while using Firefox for Android.

If Android Firefox then desktop Firefox extensions will not work on Android Firefox unless it was made for both.

Android Firefox extensions are at https://addons.mozilla.org/android/