Well, this was an unexpected and unfortunate turn of events.
I have to admit that I don’t know what the issue might be.
Please wait some more for input from other users.
In that case, when you get your live usb going again, in the installer pick /dev/sdb and use the erase and install option. The installer would take care of partitioning, flagging the partitions and installing the system and the bootloader.
This is the problem with CSM not being disabled. Some systems will install in MBR mode and the problem is users don’t seem to know the difference. When booting on the live ISO it is a totally different looking screen if it boots in UEFI compared to Bios.
Ive never created the live usb other than UEFI. It boots on both UEFI or Bios. I’m not sure even how that is done other than creating it on a system that is only Bios?