So I'm not sure how you managed to grab a PPC version of 17.04 in the first place since:
There's no such version available for download on http://cdimage.ubuntu.com/ubuntu-mate/releases/17.04/alpha-2/
Edit: found the page you must have used: Ubuntu MATE 24.10 (Oracular Oriole) Daily Build
I'm guessing that's an automated build that just hasn't come around to being wiped.
There will be no 17.04 PPC release, so thanks for your efforts but testing is not necessary.