I’ve wanted full RSS feeds for several Mastodon instances for ages.
They can be particularly useful for small instances (aka communities) with slow posting velocity—you know, that instance you wanted to join for the local camaraderie, but having/maintaining/maintaining yet another Mastodon account wasn’t worth it, the hashtag discovery wasn’t going to cut it, and trying to follow all the people in the local community individually is irksome. Well OpenRSS.org might be able to cover you.
As an example, I wanted to follow what’s happening at toolsforthought.rocks/public/local so I added that slightly trimmed local timeline URL onto https://openrss.org/ and put it into my feed reader. After they wire things together for you a bit (presuming it’s one they’ve not seen/done before), voilà your RSS feed just starts working! Now I’m following ToolsForThought at: https://openrss.org/toolsforthought.rocks/public/local.
Since my personal website works with Mastodon and the Fediverse, this last part of more easily following groups of people in my social reader helps me complete the circle of reading, following, and responding in a more IndieWeb way. (Of course I wish that Mastodon 4.0 had not gone full js;dr, which would have allowed following them using Microformats mark up with much better fidelity. le sigh)