Secure apps use smth called Google Play Integrity API. When u try to open or login inside this security app of yours, the app calls the API. Google Play Services (or microG) responds and does a server check on google’s servers to see if u meet STRONG_INTEGRITY. But since u’re not logged in with a google account it fails, since that’s a prerequisite for passing.
Either that, or the app checks its installer, sees something other than Google Play Store and says fuck u. So u need to install the app through the official Play Store, not Aurora Store or sideloading. But u can’t because the stupid play store purposefully won’t let u install new apps until u login.
So what are the solutions? U could try to use aurora store with adb/shizuku and spoof the installation source of the secure app. But that’s only local, it won’t trick google’s servers. No harm in trying ofc.
MicroG, even if u could somehow make it work on an unrooted stock samsung phone (which u can’t because it fails the cryptographic signature check that’s why u get app not installed error), still wouldn’t help. No google account = no STRONG pass, that’s how it works.
So realistically u have very few options.
Since it’s a samsung, u can’t really unlock the bootloader anymore, OEM unlock is gone. No oem unlock = no root. Temporary root wouldn’t help much, and root would prob only make it worse anyway as u’d now have to also hide it.
U could create a throwaway google account and use isolated profile, like a work profile or whatever, but that’s not a great solution. It’s basically giving up, admitting defeat. Profiles don’t perfectly isolate everything, so i would avoid this solution if possible. It’s like last resort but far from ideal.
Ur only 2 real solutions imo are either patch the app with astra/fable/opus to strip away the play integrity check and/or the app installation source check from the code, which may still not work if they check for a valid token server-side (tho it will trick the app locally), or ask ur employer to give u a work phone. If he wants u to download some secure app for work u’re fully in ur right to ask to be provided a phone.