Todd Zullinger
Another possibility is that the keys have been updated since you initially installed them and you need to remove the current key to allow dnf to import the updated key.
Todd Zullinger:
I think this is the case.
I was able to copy the yum repo file from there and install signal-libringrtc without issue. The key was imported during this install.
If you remove the key and run dnf again, it should prompt you to install the current key, which will (hopefully) work.
In other words:
$ sudo rpm -e gpg-pubkey-17280ddf
I've encountered that kind of thing before, but why does it require manual intervention? Surely there should be some mechanism for key revocation and replacement?