Thanks! ncurses-6.5 is now out and I may roll with the 'opaque' default change it makes, and this version (sys-libs/ncurses-6.4_p20240330) is essentially the same in content apart from that, so is a good stable candidate.
amd64 done
ppc done
sparc done
ppc64 done
x86 done
arm done
arm64 done
Ugh, I meant to do p20240414.