I boot my iMac from an external SSD, which is a clone of my main HDD, running Mojave. I had no issues before, recently with the Catalina being released I downloaded the update and when I choose my SSD drive I get: "this volume is not formatted as APFS".
What should I do now? I tried from recovery to convert it, but the option is disabled.
Is the only way to format it? or is there another way I am not aware of?