Issue Summary

The Text gadget was deprecated in Jira Data Center version 9.11 and fully removed in version 11.0.x to eliminate the potential security risk posed by a possible arbitrary HTML that the Text gadget might contain.
Once the user migrate to version 11.0.x, the Dashboards configured with Text gadgets starts showing rendering error.
Currently, there is no available method to perform a bulk migration of content from the Text gadget to the Rich Text gadget. 

Jira Software 9.11.x release notes
Jira Software 11.0.x release notes

Expected Results
It would be really helpful & time saving if there were an automation, script, or feature that could assist in converting Text gadget content to Rich Text gadget in bulk since it is time consuming to modify the gadgets and copying the content.

Actual Results
We need to manually go to each gadget, copy the content from Text gadget to Rich Text gadget.