TYPO3 Core

Problem ist valid, however not that easy to resolve from a global perspective - see https://github.com/TYPO3/typo3/blob/v12.4.2/typo3/sysext/core/Classes/Localization/Locales.php#L379

One solution may be to set the locale manually in GeneralUtility::formatSize() again in order to get expected output, but: the function should then separate between frontend and backend requests, since the locale for frontend requests is set in Locales.php and for backend context, only some functions in TYPO3 core respect the $GLOBALS['TYPO3_CONF_VARS']['SYS']['systemLocale'] setting and locale ist not set globally.

Since the functions main purpose is formatting a given size in bytes, it would be an option to detach locale settings from the function and add the decimal separator as argument.

Previously, the function considered the set TSFE locale (if given), see patch that removed the functionality in https://review.typo3.org/c/Packages/TYPO3.CMS/+/64045/3/typo3/sysext/core/Classes/Utility/GeneralUtility.php

Patch set 2 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/79592

Patch set 3 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/79592

Patch set 4 for branch main of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/79592

Patch set 1 for branch 12.4 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/79542