6 files declare their use of MarkupTrait in Zircon Profile 8

FieldFilteredMarkup.php in core/lib/Drupal/Core/Field/FieldFilteredMarkup.php

Contains \Drupal\Core\Field\FieldFilteredMarkup.

FilteredMarkup.php in core/modules/filter/src/Render/FilteredMarkup.php

Contains \Drupal\filter\Render\FilteredMarkup.

Markup.php in core/lib/Drupal/Core/Render/Markup.php

Contains \Drupal\Core\Render\Markup.

SafeMarkupTest.php in core/tests/Drupal/Tests/Component/Utility/SafeMarkupTest.php

Contains \Drupal\Tests\Component\Utility\SafeMarkupTest.

TwigMarkupInterfaceTest.php in core/tests/Drupal/KernelTests/Core/Theme/TwigMarkupInterfaceTest.php

Contains \Drupal\KernelTests\Core\Theme\ThemeRenderAndAutoescapeTest.

ViewsRenderPipelineMarkup.php in core/modules/views/src/Render/ViewsRenderPipelineMarkup.php

Contains \Drupal\views\Render\ViewsRenderPipelineMarkup.