Backup Installer

**Is your feature request related to a problem? Please describe.**
No

**Describe the solution you'd like**
Either for there to be an option to select the alternative/backup installer if the selected one doesn't work or isn't available ex. Shizuku isn't on, so it defaults to session installer.

**Describe alternatives you've considered**
Something like the installer automatically switching to default and back without any option when the selected isn't working. Or maybe just switching to the other installer for a time period that appears with the prompt saying shizuku isn't active.