I finally had the advice that enabled me to solve the white-balance problem for my IR images. I had been manually adjusting the Kelvin of my WB, assuming that that would surely cover all of the available points on the cool-to-warm spectrum of the WB on my R5. However if you use the shoot-to-set-WB function and shoot at something green - you get a workable balance from which to channel-swap and whatever to get the effect you want. Many thanks to Ann Miles and Jim Bennett for this.
So this is my first image with a natural-looking sky and spectral vegetation. It’s not art. But it is success!