According to JPL HORIZONS,
the sub-solar latitude on Uranus has maxima on 1946-04-03 and 2030-04-11,
and Uranus's heliocentric J2000 ecliptic longitude at those times is 77.54°.
If I put the pole coordinates from the IAU WGCCRE report
through the NED coordinate calculator,
I get a J2000 ecliptic longitude of 77.65° for Uranus's south pole.
The solstice ...
I have made an interactive simulation of Uranus and its seasons at https://ecliptiqc.ca/UranusEN.php. Playing with it, I get the north pole of Uranus pointing sunwards in early 1946 (my steps are 6 months, so I can’t be more precise for now).
The actual date may be slightly different, as I use a “fixed” orbit instead of the osculating elements, but it would ...