Revert "TESTING: temporarily remove i23 from testing"

This reverts commit 3ed1f803e03b10ebbd6e63ad27c14017b2d03c97.
TESTING: do not test MX in 8.42
Merge commit 'abb6b721ed419ed17a117d693f90f5457b14af5'
Merge -s ours from 8.42 2e71770 into master.