When using a locale switcher, we can use images but there is no option to add alt-text. That makes it impossible for people using screen readers to understand what the image is about.
Rather than using an image, we can use the locale names of course. But as it is vocalised by screen readers in one language only, we need an option to add a lang attribute to each locale.
Example:
EN (lang=en) / FR (lang=fr)
Another great option would be to add a sr-only so that each locale is read in the correct language with more comprehensive details about the link.
So for the same example:
EN (lang=en, sr-only= read this page in English) / FR (lang=fr, sr-only= lire cette page en français).
I have contacted the support team who's been very helpful but this is unfortunately something that can't be addressed at the moment.
I must say this is the only point I got from an accessibility report that could not be addressed by Webflow so I'm hopeful this will soon be fixed.