Do a clean install of the OS

On macOS download the new version from System Preferences, Software Update (or the Mac App Store) and create the bootable media with:

sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume/

using the volume that matches the name of the external drive you are using.

To install macOS from a bootable installer:

1. Plug in your bootable media.
2. Turn off your Mac.
3. Depending on your CPU:
   1. If you have an Apple silicon Mac press Power to turn on the Mac - but keep it pressed until you see the startup options window including your bootable volume.
   2. If you have an Intel-powered Mac press and hold Option while the Mac starts up - keep pressing the key until you see a screen showing the bootable volume.
4. Use Disk Utility to erase the Macintosh HD volume group (not the individual system or data volumes), shut down, and start again launching the boot options for a clean install.