After a fresh install (using maintenance/install.php command line installer on PostgreSQL) my new wiki greets me with a message:

Whoops! The default skin for your wiki ($wgDefaultSkin), vector, is not available.

Your installation seems to include the following skins. See Manual: Skin configuration for information how to enable them and choose the default.

vector / Vector (disabled)
If you have just installed MediaWiki
You probably installed from git, or directly from the source code using some other method. This is expected. Try installing some skins from mediawiki.org's skin directory, by:
Downloading the tarball installer, which comes with several skins and extensions. You can copy and paste the skins/ directory from it.
Cloning one of the mediawiki/skins/* repositories via git into the skins/ directory of your MediaWiki installation.
Doing this should not interfere with your git repository if you're a MediaWiki developer.
If you have just upgraded MediaWiki
MediaWiki 1.24 and newer no longer automatically enables installed skins (see Manual: Skin autodiscovery). You can paste the following lines into LocalSettings.php to enable all currently installed skins:
require_once "$IP/skins/Vector/Vector.php";
If you have just modified LocalSettings.php
Double-check the skin names for typos.

Here is my "skins" directory:

$ ls -al skins/
total 20
drwxr-xr-x 3 saper wheel 4096 Aug 31 01:22 .
drwxr-xr-x 15 saper wheel 4096 Aug 31 01:52 ..
drwxr-xr-x 3 saper wheel 4096 Aug 31 01:22 common
-rw-r--r-- 1 saper wheel 26 Aug 31 01:22 .gitignore
-rw-r--r-- 1 saper wheel 1160 Aug 31 01:22 README
lrwxrwxrwx 1 saper wheel 31 Aug 31 00:27 Vector ->

../../../../gerrit/skins/Vector

$ ls -l skins/Vector/Vector.php
-rw-r--r-- 1 saper wheel 3857 Aug 26 21:36 skins/Vector/Vector.php

Actually, since I7b8bd77f5868af2ccf464e48db771f2e8e0472ff (https://gerrit.wikimedia.org/r/#/c/156440/) Vector skins worked in my installer
fine, but after the installation it fails badly.

Should this line:

require_once "$IP/skins/Vector/Vector.php";

be added automatically by the installer? Where does autodiscovery belong now?

https://www.mediawiki.org/wiki/Manual:Skin_autodiscovery promises:

The bundled skins which come with MediaWiki (like Vector or MonoBook) will continue to be updated with the MediaWiki Core. When you upgrade your installation to MediaWiki 1.24 or newer, you will also get a new version of these skins. (You should then remove the old copies from the skins/ folder, see Manual:Upgrading#Files remaining that may cause errors.)

... but this no longer seems true...

Version: 1.24rc
Severity: major