I don't really think that convergence has been much of an
issue since slotmasks became the norm many years ago,
as these are inherently self converging.

LOL! I am holding a service manual for a Sony slot-mask
Trinitron monitor featuring 3 pages of instructions on how
to accomplish what you call "self-convergence".

There is nothing inherently "self-converging" about slot-mask CRTs.

The original "delta" gun pattern required a fairly elaborate convergence
process. In the early '60s, GE introduced an "in-line" gun arrangement (the
first of its kind, AFAIK) that had less lateral misconvergence than the
delta design, and thus a simpler setup.

Sometime in the '70s, I think (CMIIW), the precision in-line (PIL) system
was introduced. The deflection yokes were deliberately miswound (using a
plastic former with ribbing that precisely positioned the wires) to distort
the deflection and thus produce correct convergence with minimal
adjustments.

I'm typing this missive at ViewSonic PerfectFlat A95f monitor that has
perfect (and I mean perfect) purity and convergence right to the very
corners. The tube is a Diamondtron, Mitsubishi's version of a Trinitron.