Unable to change language name

still an issue in 10.2.4

Needs steps to reproduce

As the OP mentioned, the steps to reproduce, as of Drupal 10.2.4 are:

- install Drupal using for example German as a first default language
- enable English
- do some stuff, create content, etc.
- enable UI, config and content translations

(maybe all of the above steps aren't necessary to reproduce the bug)

then:
- go to languages /admin/config/regional/language and change the label of both languages, for example, name Deutsch "de" and English "en"

maybe it will first appear to work. maybe not.
if you do something else, like adding content in one or the other language, one might jump back to the original name "Deutsch" or "English".

The strange thing is that the YML config item shown by DEVEL is all correct.

If trying to add translations to the language names, an error message will appear "English translation was not added. To add a translation, you must modify the configuration."

Sometimes there is no error message, and the translation seemingly gets accepted, but the name of the language will jump back to the original anyway, even if on the languages page /admin/config/regional/language everything seems normal and both are displayed as "de" and "en", but either Deutsch or English will appear as its original name no matter what settings.

after doing something else on the site, ONE of the labels on the languages page /admin/config/regional/language will revert back to original.

it's very frustrating.

this bug has been going on for years and has been reported in one form or another many times.

I wrote more about it here:
https://www.drupal.org/project/drupal/issues/3337864#comment-15540567 🐛 Configuration language is not adjusted after changing the site default language Active

If there are two issues and the other has more information we should close this as a duplicate.

there are a dozen or so of related issues

@DrupalDope are the issues related or duplicates? If they are duplicates, it is more likely to be resolved if all but one are closed, so that all work is being done toward the same resolution.

@pameeela
if I knew if the bugs were related or duplicates, it would mean I knew the exact nature of the bug, but I don't.

The problem is described here:
https://www.drupal.org/project/drupal/issues/2797961#comment-15629652 🐛 Language switcher label cannot be changed for English Active