Cannot install eca 2.1.x-dev using composer

You may need to use minimum-stability: dev in your composer.json

However, it installs fine for me on a fresh D11 project with "minimum-stability": "stable".

x@Mac drupal-11 % ddev composer require 'drupal/eca:2.1.x-dev@dev'
./composer.json has been updated
Running composer update drupal/eca
Loading composer repositories with package information
Updating dependencies
Lock file operations: 4 installs, 0 updates, 0 removals
  - Locking dragonmantank/cron-expression (v3.4.0)
  - Locking drupal/eca (dev-2.1.x 3b3b975)
  - Locking mtownsend/xml-to-array (2.0.0)
  - Locking webmozart/assert (1.11.0)

composer require "drupal/eca": "2.1.x-dev@dev"

In PackageDiscoveryTrait.php line 383:

Could not find a matching version of package 2.1.x-dev@dev. Check the package spelling, your version constraint
and that the package is available in a stability which matches your minimum-stability (dev).

this is strange.

It must just be my system.

This is a composer support request, not an ECA bug report.

If composer can't find something, or runs into constraint issues, what often helps is to use composer why-not [PACKAGE] [VERSION], it should tell you why something can't be installed.

I also wonder why you would require the dev release?

And the message in the IS states, that ECA 2.1 is already installed. The lock file has it as version 2.1.7, and now you want to require the dev release. Composer may be of the opinion that 2.1.7 and 2.1.x-dev are in conflict. Or, there might be something else in the dependency tree that requires 2.1.7, which would then prevent 2.1.x-dev to be installed.

Again, all about composer constraints and your project structure.