I installed Ventura 13.7.1 on a 1TB Crucial external USB-c drive. When I boot to the internal iMac HDD running Ventura 13.7.1 the USB-c drive is mounted and accessible. When I use the Option key to select the USB-c or select it as the startup drive in System Settings the iMac will revert to the internal HDD each time. Is there a setting I am missing or an incompatibility issue?
iMac 21.5″, macOS 13.7
I boot from an external SSD into High Sierra, Mojave and Ventura without issue because I cloned my internal drive to the external SSD with Carbon Copy Cloner. The demo version of CCC should work.
This user tip show how: Using Carbon Copy Cloner to Make a Bootable Clone of an Intel Mac - Apple Community
I boot from an external SSD into High Sierra, Mojave and Ventura without issue because I cloned my internal drive to the external SSD with Carbon Copy Cloner. The demo version of CCC should work.
This user tip show how: Using Carbon Copy Cloner to Make a Bootable Clone of an Intel Mac - Apple Community
My 21.5" iMac will only allow me to boot from an external USB drive if I disconnect all other USB devices except the drive from which I am attempting to boot. Otherwise, it always resorts to booting from the internal drive.
I don't know if this is the case for your system, but it might be worth a try.
2017 i5 21.5 iMac won’t boot to external USB-c
