Can't upgrade from Ventura to Sonoma: 'The volume cannot be downgraded'
The disk to install to is greyed out and when clicked on it says 'The volume cannot be downgraded'. Which is of course weird because I'm actually upgrading.
I also tried to do it via a USB bootable Sonoma installer but I get the same message and a greyed out disk.
NOTE: When trying to upgrade to Sequoia I don't get the the message (drive is also not greyed out), but with a relatively older Mac I'd rather have one OS version earlier (I'm probably being overly cautious, but it is what it is).
Any ideas?
Macbook Pro 2018 running Ventura 13.7.1
MacBook Pro (2017 – 2020)