SBT won't run chisel tutorial... can't seem to find proper scala version - scala

Question

I installed OpenJDK and then SBT on my Fedora 28 system.
SBT 1.2 comes from the bintray--sbt-rpm repository (the official one).
Both seem to work fine, and I can do basic scala projects.
Then I cloned the chisel-tutorial from the github chisel-tutorial site.
But when I go into the chisel-tutorial directory, SBT refuses to run at all, getting what appears to be an error about the scala version (which is well-nigh incomprehensible to me, but zillions of posts imply that scala version mismatch causes this message):
java.lang.NoSuchMethodError: scala.Predef$.$conforms()Lscala/Predef$$less$colon$less;
My understanding is that sbt is supposed to find the right scala version, but in my case it clearly does NOT.
I have tried dozens of things, some hinted at by posts that refer to the above error message. But they never say exactly what to do, just say something like "your problem is scala version, and that should fix it".
Surely there are chisel users who know the answer, or sbt aficionadoes who do.
Any help would be appreciated!