@smoooo I replied to your pm with the script I use to expand OSX partitions.
Also, the prohibitory symbol (crossed out circle) could also mean an incompatible OS for the hardware, I do a little bit with snow leopard to make it work on unsupported hardware, and it usually involves a kernel swap at a minimum to get old OS’s booting on new hardware.
Not sure if youre still having issues with corestorage or not, but “diskutil cs list” will show you your corestorage groups, which would typically need to be deleted before cloning or modifying partitions (you would get the prohibitory symbol from this too).
Also, just as a random tidbit, you can install OSX on an HFS+ disk all the way up to 10.13 (never tested 10.14+, might still work) if you run the installer from the commandline and use the
–converttoapfs NO
switch for the installer. This might give you a LITTLE bit more flexibility as far as being able to read partitions/volumes from linux utilities (APFS support is much harder to come by).