Having same issue on my R100RT. Today I ordered window tint film to try and see if it stops the glare. Will report back with results. A friend suggested that I ride west or only at night.
To be continued...
Picked up some 35%, least blocking, window film from a business that installs on cars. Picked up approx. 1 sq. ft. Covered the speedo to compare against un-covered tach. Tried it today, the glare was reduced, but not completely eliminated. Can still read dial, odometer and back lighting still noticeable. Will leave in place for awhile. Good luck.