There are two remaining uses of the 7.4-based publish flavour of the MediaWiki app image:
- The mw-debug pinkunicorn release [0] - i.e., "regular" k8s-mwdebug.
- The mw-script main release [1] - i.e., the image used when the tool is invoked with --php_version=7.4 (see T387917: Migrate mw-script to PHP 8.1).
For #1, there's arguably not much benefit to continuing to operate pinkunicorn on 7.4, since there are no production traffic-serving use cases running those images anymore. Further, the continued use of 7.4 there could potentially be a source of confusion.
For #2, we'll want to wait a little bit before removing the --php_version fallback (the default changed to 8.1 yesterday, 2025-04-02). I need to think a little bit on how long.
It may also be that we want to wait on #1 until we do #2, on the basis that we want to have at least some basic confidence that the 7.4 image still "works" by some definition thereof.
Once we remove both of those use cases, we can then remove the publish flavour from build-image.py [2] to stop building it entirely (edit: after also switching train-dev to use 8.1).