@infograf768 jm, I tested this with him via zoom and JP installed/uninstalled on my 3.8.3 site but didn't on his. english-au did however. His site IS Multilingual. We checked trash, and cleared caches, checked for the language being used in some menu/content/item but nothing changed. The behavior I saw was very strange so I had him open a ticket directly.

Issue confirmed.

System information

3.8.4-dev
Multilanguage Site (4 Lang.) & Test English (GB) Sample Data
macOS Sierra, 10.12.6
Firefox 57 (64-bit)

MAMP 4.2

• Apache-Server
• PHP 7.0.22
• MySQLi 5.6.35

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  _{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/19265.}

Looking now

I was trying to uninstall Japanese without the language filter ("Japanese Language Pack") and it finally worked - i then tried to find out if there was such a package also for "english AU" and there was the main package left, just not the extensions which i already removed.

Looking at the error, it looks normal if one tries to uninstall by language and not by package in recent lang packs

en-AU has not been updated (alas) to the new settings we have asked TTs to use in their manifest.
<blockChildUninstall>true</blockChildUninstall>

@infograf768 jm, the behavior is inconsistent. in en-au he was able to uninstall the language sets individually but that left the pack. with jp it refuses to allow individual removal but does remove via the pack.

@N6REJ
Look above #19265 (comment)

Closing issue as not core.

@infograf768 yeah, was typing as you typed that :P tnx