Installling Matomo via composer should ship the TagManager plugin or notify about next step to get the complete installation
When creating a new Matomo instance via
composer create-project matomo/matomo
the directory ./plugins/TagManager is empty.
total 8.0K drwxrwxr-x 2 ubuntu ubuntu 4.0K Dec 27 10:31 . drwxrwxr-x 95 ubuntu ubuntu 4.0K Dec 27 10:31 ..
DISTRIB_ID=Ubuntu DISTRIB_RELEASE=22.04 DISTRIB_CODENAME=jammy DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS" PRETTY_NAME="Ubuntu 22.04.1 LTS" NAME="Ubuntu" VERSION_ID="22.04" VERSION="22.04.1 LTS (Jammy Jellyfish)" VERSION_CODENAME=jammy ID=ubuntu ID_LIKE=debian
PHP 8.1.11 (cli) (built: Sep 29 2022 22:29:14) (NTS) Copyright (c) The PHP Group Zend Engine v4.1.11, Copyright (c) Zend Technologies with Zend OPcache v8.1.11, Copyright (c), by Zend Technologies
Composer version 2.4.2 2022-09-14 16:11:15
That would never work - composer doesn't handle git sub modules. TagManager needs to be published as package, which it's not, and added as a dependency in composer.json for matomo.
I am no fan of git sub modules at all - and the recommended approach for matomo should be to remove all sub modules and add them as packages instead.
My 2 cents are on a post install script that clones all the sub modules:
True, you could use a "post-create-project-cmd" event in composer.json that checks out the git sub modules. Still, I do think they shouldn't be git sub modules, at least they should be on packagist, so you could use whatever approach to install them.
I don't think setting up Matomo using composer create-project ever worked as expected. It's not only the submodule plugins, but also any other plugin.
I would personally discontinue and remove the package from composer, as it would require some more effort to get that running correctly I guess.