TYPO3 10: Backend RTE does not allow links to typo3 pages

Happened with custom RTE configurations.

Solution was to include the TYPO3 ckeditor RTE plugins:

+++ public/typo3conf/ext/myext/Configuration/RTE/Article.yaml
+++ public/typo3conf/ext/myext/Configuration/RTE/Article.yaml
@@ -21,3 +21,4 @@ editor:
 imports:
   - resource: "EXT:rte_ckeditor/Configuration/RTE/Processing.yaml"
   - resource: "EXT:rte_ckeditor/Configuration/RTE/Editor/Base.yaml"
+  - resource: "EXT:rte_ckeditor/Configuration/RTE/Editor/Plugins.yaml"