Please review the link below for guidance on due dates related to individuals in disaster areas:  

https://www.irs.gov/newsroom/irs-extends-may-17-other-tax-deadlines-for-victims-of-tennessee-storms-...

While I recognize this guidance is aimed at individuals specifically, I think it can provide guidance in your scenario.  This press release from the IRS states, "Disaster area individuals who need more time to file, beyond these postponed deadlines, can get it by submitting a request for an automatic extension. This will extend their filing deadline until October 15, 2021. The IRS emphasized that this additional extension is not an extension of time to pay."

I hope this helps you determine the correct extended filing date for the trust.