TYPO3 10.4 - Locale "en_US.UTF-8" not found

I've got a problem with the language localization in TYPO3. The site works fine, I don't get any warnings or erros in the 'normal' TYPO3-log in the backend. But every minute I got a new line in sitename/var/logs/typo3_abc.log saying

Thu, 23 Jul 2020 13:14:55 +0000 [ERROR] request="4fc10d4752ec5" component="TYPO3.CMS.Core.Localization.Locales": Locale "en_US.UTF-8" not found.

This is my config.yaml

languages:
  -
    title: English
    enabled: true
    base: /
    typo3Language: default
    locale: en_US.UTF-8
    iso-639-1: en
    websiteTitle: ''
    navigationTitle: English
    hreflang: en-US
    direction: ''
    flag: en-us-gb
    languageId: '0'

Any hints or suggestions what is missing?

My system: TYPO3 Version 10.4.5 as a container with php:7.2-apache.stretch and MariaDB Version 10.2 .

Solution

clean declaration, but does it match to your available locals?

check the list of available locales with locale -a in a shell on your system.

maybe it is written a little bit different like en_US.utf8 or en_US.utf-8 or en_US.UTF8 or ...