Lemme math some. DOD is 3/30/2023. So we want a FYE 2/29/24. That's 12/31 plus 2 months, so unextended 1041 would be due 4/15 plus 2 months is 6/15. Extended due date is 9/30 plus 2 months is 11/30. Bummer.

Why do you think that for tax filing, it looks like an estate? Anything titled in the name of the trust gets reported on the trust's 1041 with a 12/31 year-end. Anything not titled in the name of the trust gets reported on the estate's 1041 with a 2/29 year-end. Both of them are delinquent, sorry out of luck. If the trust made distributions to the beneficiaries during 2023, you're gonna have some sad benes.

The 645 election just lets you combine those two returns into one 1041. Without it, you're stuck filing both returns.

Whatever distinction you're trying to draw with the comments about revocable vs irrevocable isn't relevant, IMHO - or if it is relevant, I don't understand what you're getting at.