I'm pretty sure that "failed to verify" means that after it downloads, it scans the file to make sure it exactly matches what was expected. There might have been an error in transmission causing something to not match, or the source you downloaded from could have a different copy.
I just tried it on my phone, and it installed fine. Try downloading it again.
In the settings, my repositories are -FUTO: (app.futo.org/fdroid/repo) -F-Droid: (f-droid.org/repo)
and that's it. Is that what you have as well?
Tool? upvoted