"Language dropdown lists vary on X-Subdomain and X-CS" and "Listed high priority languages [, which] are similar to language dropdowns": I don't understand if this is a proposed or existing thing, but it seems to duplicate ULS features in some way; their logic should probably be coordinated, at least when ULS replaces the standard interlanguage wikilinks view (ask Pau)?
Topic on Talk:Requests for comment/Zero architecture
Thanks, Nemo. They dropdown list and the listed high priority languages is a feature of the pre-existing Wikipedia Zero's Special:ZeroRatedMobileAccess page (we've made small tweaks since taking on the codebase, but it's largely the same). Will check with Pau about ULS.
This post was posted by ABaso (WMF), but signed as ABaso(WMF).