It's a pain to phrase, but: There is no reason to use the Swiss flag to indicate a language. French has the French flag. German has the German flag. Etc. There are dialects, as a nuance to this, but you can solve that by e.g. using a 50/50 merge of the German and Swiss flags.
Countries may have ambiguous languages, but _languages very rarely have ambiguous countries_. Sure, there are Finnish speakers in Sweden, but the Swedish flag remains a clear indicator of the Swedish language.
Hindi and India is the main exception to this. Arabic is also difficult, though Egypt seems to have a slight edge by convention.
> UX/UI designers have rightfully been banging the "don't use country flags to indicate languages" drum for literally decades
I sympathise, and if they have any better ideas than a textual list that users need to read through rather than quickly scan (not very good UX...), I'd love to hear them. From a _UX perspective_, is there something better than the flag cloud at https://nuenki.app for quickly asking "is my target language supported"?