I got an email from Abdulaziz (Admin of R2 project) today saying that there's possibly a new SNP found under the R-M479 tree that is not R-M124, I see it here:
https://www.yfull.com/tree/R-M479/
I'm wondering if all of the current M479+ / M124- folks fall under this new branch. If so then we have an R2a and R2b based on old terms.