The following design sketch is suggested to be implemented:
Such as on Wikidata, on the very top have the language icon with the current setting next to it (e.g. English). This is clickable / tappable.
When actioned on, we get a modal with a text ("Select a language"), a language selector (based on our ZObjectSelector but restricted to languages), and a cancel action (e.g. a X in the corner or a cancel button) and an action button (Switch? OK?) that activates once a language is selected.
Once the language is selected, it takes us to the version of the given page in the respective language (The respective patterns are currently being implemented in T268678 )
It is OK if that link for now only works in Vector22 and is not immediately supported in Minerva. We will set up the default mobile skin to be Vector22. It has to work in both Vector22 and Minerva.