As a third-party wiki administrator, I deploy a lot of third-party extensions. But, currently, update.php script of LU always tries to update all translations from the specified repository.

For example,

$wgLocalisationUpdateRepositories = [
	'github' => [
		'mediawiki' => 'https://raw.github.com/wikimedia/mediawiki/master/%PATH%',
		'extension' => 'https://raw.github.com/wikimedia/mediawiki-extensions-%NAME%/master/%PATH%',
		'skin' => 'https://raw.github.com/wikimedia/mediawiki-skins-%NAME%/master/%PATH%'
	],
	'femiwiki' => [
		'extension' => 'https://raw.github.com/femiwiki/%NAME%/main/%PATH%',
		'skin' => 'https://raw.github.com/femiwiki/FemiwikiSkin/main/%PATH%',
	],
];

sudo nice -n 19 php update.php
sudo nice -n 19 php update.php --repoid femiwiki

The first line in the above commands updates all Wikimedia-related translations but fails and skips updates for third-party extensions of 'femiwiki'.
The second line tries to update all components, MediaWiki core, MWF-deployed extensions and skins from that 'femiwiki' organization, fails, skips, and only successfully updates few extensions that belong to 'femiwiki'.