/filter/tips returns Drupal\Component\Plugin\Exception\PluginException: Plugin (filter_dopl) instance class "Drupal\dopl\Plugin\Filter\Dopl" does not exist. in Drupal\Component\Plugin\Factory\DefaultFactory::getPluginClass()

Problem/Motivation

Lets start with the first D8 / D9 issue:

on /filter/tips:

Drupal\Component\Plugin\Exception\PluginException: Plugin (filter_dopl) instance class "Drupal\dopl\Plugin\Filter\Dopl" does not exist. in Drupal\Component\Plugin\Factory\DefaultFactory::getPluginClass() (line 97 of core/lib/Drupal/Component/Plugin/Factory/DefaultFactory.php).

Drupal\Core\Plugin\Factory\ContainerFactory->createInstance() (Line: 76)
Drupal\Component\Plugin\PluginManagerBase->createInstance() (Line: 81)
Drupal\Core\Plugin\DefaultLazyPluginCollection->initializePlugin() (Line: 76)
Drupal\filter\FilterPluginCollection->initializePlugin() (Line: 54)
Drupal\filter\FilterPluginCollection->getAll() (Line: 83)
Drupal\filter\FilterPluginCollection->sort() (Line: 144)
Drupal\filter\Entity\FilterFormat->filters() (Line: 333)
_filter_tips() (Line: 30)
Drupal\filter\Controller\FilterController->filterTips()
call_user_func_array() (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 578)
Drupal\Core\Render\Renderer->executeInRenderContext() (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext() (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 158)
Symfony\Component\HttpKernel\HttpKernel->handleRaw() (Line: 80)
Symfony\Component\HttpKernel\HttpKernel->handle() (Line: 57)
Drupal\Core\StackMiddleware\Session->handle() (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle() (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass() (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle() (Line: 50)
Drupal\ban\BanMiddleware->handle() (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle() (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle() (Line: 49)
Drupal\remove_http_headers\StackMiddleware\RemoveHttpHeadersMiddleware->handle() (Line: 23)
Stack\StackedHttpKernel->handle() (Line: 716)
Drupal\Core\DrupalKernel->handle() (Line: 19)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes