I think we need a new word. You see, to pedants like me, a folk musician should play folk music and folk music has been defined (see other threads). We also have very pleasant singarounds, song sessions, and sessions (note the Oxford or Harvard comma) at which quite a lot of music that is not folk music is played, listened to and enjoyed. That music is however distinguishable from other more populist types which (English and US readers will disagree over whether there should be a comma before "which") usually revolve around more amplification and have developed from, in many cases, different sources.

In practice the performers of this unnamed music are usually welcomed. It is the perfectly correct observation that what they are doing is not "folk" that gives the incorrect impression of exclusion.

I have previously suggested "New Folk" by analogy to "New Country" quite a lot of which is no longer new and quite a lot of which was never country.   Any better ideas?

I think this is worthy of a separate thread, Richard. Would you care to do the honours?