I would like to use the new mechanism to invoke this extension without spamming my error log. Thus it will be great if someone could have a peep at this. Thanks and cheeers

@Glaisher

Thanks a ton for clarifying: So when adding the following to "LocalSettings.php" I indeed do no longer get these PHP Notices:

wfLoadExtension( 'TitleBlacklist' );
$wgTitleBlacklistSources = array(
	'http://www.example.org/w/index.php?title=MediaWiki:Titleblacklist&action=raw',
	'https://www.mediawiki.org/wiki/MediaWiki:Titleblacklist&action=raw',
	'https://meta.wikimedia.org/w/index.php?title=Title_blacklist&action=raw'
	);

The only thing I still have to figure out is why only the local Titleblacklist works, but that's probably another story. I will adjust the extension's documentation accordingly.

@Glaisher

I have just just documented this. It will be nice if you could have a peep at it.

Actually it should be like the following (note that the constants' values are directly used):

$wgTitleBlacklistSources = array(
	array(
		'type' => 'localpage',
		'src'  => 'MediaWiki:Titleblacklist',
		),
	array(
		'type' => 'url',
		'src'  => 'https://meta.wikimedia.org/w/index.php?title=Title_blacklist&action=raw',
		),
	);

Sorry I was unclear on that part. I guess that's why only the local blacklist works. I've also updated the documentation.

Ah, I get it. Thank you! Since I am not a coder I misinterpreted your comment.

This does not solve the issue why external urls do not work, still only the local one steps in but this is another story and does not belong in this task.

Could you open a new bug with error logs and anything else that could be helpful with debugging?

Yep, I have created T129492 for this. Hopefully it is just a tiny issue.