Thank you. I do remember using Virtualbox now but it was ages ago. I'll just leave it for the moment.I just checked my MacBook, nothing or the sort listed on mine.
Thank you. As for Raspberry Pi Imager it says the SD card only has a very small storage amount which I think is because the whole card has got messed up. The card is actually a 256GB card so I think the partitions are borked.Try Raspberry Pi Imager which has options to erase SD Cards as well as various install options. As to why Disk Utility isn't working, I've found it be awkward when using file systems other than Mac based ones
I can see the partition on the diskutil list command but I can't delete it. I've tried both eraseDisk and secureErase. The partition is shown as 32MB so I need to delete the entire partition map and start again.Do you have a Windows machine kicking about? You can use DiskPart to clear the drive.
You can do it in Terminal too, something like:
diskutil list
diskutil eraseDisk free none /dev/makeSureYouSelectTheRightIdentifier!
...and if you want to zero it out:
diskutil secureErase 0 /dev/makeSureYouSelectTheRightIdentifier!
EDITed to add, if you want to add the screenshot of 'diskutil list' we can talk you through it if it would help?