Instructions for Mediawiki 1.27

[AladW]

Is this mediawiki 1.27 supported at all? (The mediawiki page mentions 1.30.) I'm using git master because no releases appear available, and get the following error on using the installation instructions:

[Thu Oct 25 12:30:54.120134 2018] [:error] [pid 16893] [client ...] 
PHP Fatal error:  Uncaught Exception: /var/lib/mediawiki/extensions/CrossReference/extension.json does not exist! 
in /usr/share/mediawiki/includes/registration/ExtensionRegistry.php:90\nStack trace:\n#0 
/usr/share/mediawiki/includes/GlobalFunctions.php(115): ExtensionRegistry-
>queue('/var/lib/mediaw...')\n#1 /etc/mediawiki/LocalSettings.php(133): 
wfLoadExtension('CrossReference')\n#2 /usr/share/mediawiki/includes/WebStart.php(124): 
require_once('/etc/mediawiki/...')\n#3 /usr/share/mediawiki/index.php(40): 
require('/usr/share/medi...')\n#4 {main}\n  thrown in 
/usr/share/mediawiki/includes/registration/ExtensionRegistry.php on line 90

LC_ALL=C stat /var/lib/mediawiki/extensions/CrossReference/extension.json
  File: /var/lib/mediawiki/extensions/CrossReference/extension.json
  Size: 678             Blocks: 8          IO Block: 4096   regular file
Device: 803h/2051d      Inode: 7874149     Links: 1
Access: (0640/-rw-r-----)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2018-02-26 15:32:45.000000000 +0100
Modify: 2018-02-26 15:32:45.000000000 +0100
Change: 2018-10-25 12:29:24.595615606 +0200
 Birth: -

Note: the host is Debian 9.