Using the Civi interface to test sending a thank you email with Financial Type = Endowment Gift gives a 500 error and no email. The normal Financial Type = Cash works fine. This happens on both Production and Staging. Elliott confirmed he sees the same, but couldn't see details in the logs.
I tried making a test donation with utm_medium=endowment, and that did get me the right email.
This is blocking me from testing T232121: Update Endowment automatic thank you email