Javascript select list to change keyboard layout for different languages

How to change keyboard layouts with JS via a select element for different languages, e.g. Greek, French, Spanish, etc.

I would need help not only with the JavaScript but with the different keyboard layouts and languages.

Start by clarifying the desired behavior for the select element and which Greek, French, Spanish, and other keyboard layouts are required. Then inspect the virtual keyboard's existing JavaScript entry points and determine how layout selection should be represented; done means the selected language reliably changes the keyboard layout.

Written by the indexing model from the issue text.