Thanks for that.
The info' looks fine and if you got Scribus from the official site then you're most probably using the right version.
(You're using a slightly old version of Ghostscript but that shouldn't cause whatever problem you're having. Copy/paste text shouldn't touch Ghostscript.)
My "strange error message" issue was probably a red herring.
I can't understand why just pasting the text from a text editor would cause the same problem. I've just pasted the full text of "Frankenstein, or The Modern Prometheus" (438KB) into a text frame and Scribus didn't complain at all so I can't see how it can be a "size thing".
This is starting to be annoying, but in a good "I want to figure this out" kind of way.
It's odd that you're not having the issue with other copies of the software. Have you tried re-installing Scribus? It might just be some weird hardware/software corruption somewhere. It's easy enough for a single bit on the disk to be toggled and the software still looks like it's working (see, for example, https://www.necam.com/docs/?id=54157ff5-5de8-4966-a99d-341cf2cb27d3
if you really want some light bedtime reading! ).
It's a shame you're having such trouble with Scribus when you're evaluating it. People coming from commercial software is always good for Scribus so it feels bad when you're having this kind of awkward problem with something that should be straightforward.
I'll let my brain stew on this but, for now, I'm stumped. (Maybe I'm thinking too hard about it and the solution is simple.)