This is fascinating work and sounds a little like the research my daughter says she wants to study (she's only a sophomore at UMBC right now, though). She hopes to get an internship in the summer of her junior year. She is interested in plant biology and bioengineering.
If I understand correctly, plants have RNA - would this mean new RNA-based lifeforms could also be found within plants?
There is a hypothesis that once upon a time life passed though an RNA only stage without DNA and proteins. RNA world https://en.wikipedia.org/wiki/RNA_world
The premise of TFA is that we're treating viruses and virus-like things as a class of lifeform. There are RNA viruses, and these obelisk things are also RNA-based. Presumably that's what OP is asking about with regard to RNA-based lifeforms.
If I understand correctly, plants have RNA - would this mean new RNA-based lifeforms could also be found within plants?