Posted this to the Power Platform Community forum:

Lost the best part of an hour testing and trying to fix a Child Flow returning true to the parent via “Respond to an App or a flow”. I’m trying to test that output with a Condition and it would not work. I tried setting the output on “Respond to…” to text and yes/no. Tried with single quotes, without quotes, using Expression to pass boolean TRUE on BOTH sides (in the output and the Condition value).

I could see from looking at the results of the Flow it looked like it was returning a String but the Condition step gives no debugging output – you can’t see what it is comparing, never mind the Type!

In the end, I figured some magic auto-typing was happening somewhere and simply changed the output from the child to Text with the value yes (no quotes) and set the value of the Condition in the parent Flow to the same.

Worked immediately.

Wonder if I was actually doing it wrong?