For anyone trying to get this (really very awful) app to work without saying "Threat detected" and complaining about running on a Jailbroken / Rooted device (once you decode the error id), the steps outlined in the excellent compatibility post below to disable secure app spawning make it work for me. This is not a great solution, but there isn't much I can do about it, as its mandated for work :(
For reference im on a Pixel 7 with the latest Android 15 build. I am running RSA Authenticator v4.5.1.1, which was installed using Aurora. Past versions of the app worked for me without having to change any settings.
https://discuss.grapheneos.org/d/8330-app-compatibility-with-grapheneos