@Simon Bang Pedersen - SIPE Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
I understand that you want to pull the "userEmailAddress" of the user who has approved or rejected the send approval email action in your logic app.
If my understanding is correct, then try making the below changes to the Send Approval Email action in your logic app.
I have made the above changes and tested in my local environment; we are able to receive the approved person user email id without any issues.
Here is the sample output screenshot for your reference:
Hope this helps, let me know if you have any further questions on this.
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