Is there a way to install the Shopware demo data (not the random demo data) after an installation of the dev template?
Yes it is possible.
Solution 1:
You are able to run the first run wizard in the dev template.
This can be done from Settings > System > First run Wizard here you will have to say "next" to the first step where it asks to install language package. At second step, you can install the demo data.
Just close the window or F5, after installing demo data plugin, you dont have to go through the whole run wizard again.
Solution 2:
composer require store.shopware.com/swagplatformdemodata