Hi all,
I know there was a topic (in archives) asking for a RSS feed providing, and that the staff already responded that Muut (the technology behind this forum) doesn’t allow for RSS creation due to a complex page generation.
Thankfully, I found the only RSS online feed provider able to make it work 
: https://rss.app/rss-feed
You’ll need to register first in order to create feeds, and then you can paste your links. Just for the record : they use a non-credential login, so each time you want to retrieve your account, you need to click “login” and they send you an e-mail with a connexion link. And then you can reach your online account (they only store your e-mail and feeds).
Except that, it works perfectly : click on “Webpage to RSS feed” (they propose many apps, to make most famous websites to work directly), paste the link to the Grav forum ( https://discourse.getgrav.org/latest ), and click “generate”. Then, paste the generated link into your RSS software.
All other providers I tested failed. This is the only one working ! 
PS : I also tested all RSS softwares on Windows (included “GreatNews”), and the final one I chose, for its perfect UI, is QuiteRSS. Its options are extended too.