It depends on who you’re referring to as a casual user. My mother for example would certainly have a hard time with it, then figuring out the key to bring up the boot menu (and being faced with a scary dialog that they’ve never seen), then selecting the right device, then likely being faced with GRUB which would also look scary to her, and by then she’d be overwhelmed before even getting to the install portion.
It depends on who you’re referring to as a casual user. My mother for example would certainly have a hard time with it, then figuring out the key to bring up the boot menu (and being faced with a scary dialog that they’ve never seen), then selecting the right device, then likely being faced with GRUB which would also look scary to her, and by then she’d be overwhelmed before even getting to the install portion.