After seeing your comment about 990-T now able to be E-filed, I have tried to E-File one of my 990-T returns.  The return was sent, but ultimately rejected saying the type listed under the return info in Screen 1 is missing or invalid.  However, when I look at the input for the diagnostic referenced, I have listed     408(e) - IRA, SEP or SIMPLE, which is correct.  

I guess the E-Filing really isn't working yet 😞

Did you have any other errors besides the Form to be attached?