Split from T271918
In Firefox on Android, the web app is completely broken in RTL, although it works well if my UI language is English. The first step of choosing the section shows a mostly blank screen. In Chrome on Android it works as well as on the desktop, and in Firefox on desktop it's mostly good, too. Screenshot:
Tested on testwiki wmf.23 - the issue is confirmed on Firefox 97 on Samsung Galaxy 8 (360 x 740). The UI doesn't fit the screen - technically, all elements are there but Special:ContentTranslation# is not usable:
The guidance wizard example - a user won't see the image centered, instead a screen with some grey background will be displayed, and the last screenshot shows that only with significant zoom-in, the all elements will fit the screen:
Expected  |  |  |