It is not possible to use normal custom symfony workflows when the eZ workflow bundle is installed.

Reproduce:

1. Define any workflow or state machine under framework.workflows in config.yml or equivalent.
2. Try to trigger a transition on the workflow
3. EzSystems\EzPlatformWorkflow\Exception\NotFoundException happens

The problem is that:

• There is a separate workflow registry for eZ, which contains workflows from the eZ config and symfony has its own registry
• When calling apply, then eZ's \EzSystems\EzPlatformWorkflow\Event\Subscriber\WorkflowGuardSubscriber subsriber runs the workflow.guard event, which tries to get the workflow object from the eZ registry
• Because its not an eZ workflow, a NotFoundException is thrown by the $this->workflowRegistry->getSupportedWorkflow() call

Other subsribers may do the same, but workflow.guard is the first event and I didn't check further.

Solution:
On NotFoundException the workflow subscribers should just return and don't do anything.

Example workflow can be extracted from the official docs: https://symfony.com/doc/3.4/workflow/usage.html