That is because there is no entry in the _workflow_associations table

The only code that exists to create the entries for existing content is in the update sql

@alikon
Please look at my POC for multilingual sample data where I point to the issues with the new workflow system.
#21553

i've already looked at that pr ....but here i'm talking about a step before ie when you install with sample data withot multilanguage or using the sample date plugin

even then i got the same error 500 JHtml workflowstage not found.

The blog sample data is absolutely not modified to use workflow.

if it was only that

Yeah, agree.

The sample data uses the article model to create the articles. If that doesn't also set the correct workflow states, then something is wrong with workflows. The model or workflows should handle that. There should be no change in sample data. It can't be that we have to go through each workflow stages when creating items programatically, that would make it an impossible task.

Set to "closed" on behalf of @franz-wohlkoenig by The JTracker Application at issues.joomla.org/joomla-cms/21564

closed as having Pull Request #21681

#21681 will not solve installing sample data (Blog or multilingual) from the sample data module.

@infograf768 please open a new issue if there is not already one open,
this issue was only about sample_testing.sql not for the sampledata module/plugin....