In order to activate the Paste Plain Text Option in the Froala WYSIWYG HTML Editor navigate to Settings >> Advanced Settings:
Froala Plain Paste
System Variable: froala_plain_paste
By default this setting is turned off, when this option is enabled, the Froala WYSIWYG HTML Editor filters the pasted content and keeps only plain text by removing all its rich formatting.
The advanced setting froala_plain_paste will impact the following classes:
By default it's active for: