I had the same problem doing a default install (ie erase disk and install Ubuntu. No fancy resizing, selecting own partitions etc hence not duplicate of #1766945). But I did select LVM.
Repeated the installation but this time I first ensured I was connected to the internet with a wifi connection and then allowed downloading of updates during the installation. Installation was successful.
Possible caveat: I am booting in insecure mode. Not sure whether that makes a difference.
Workaround:
I had the same problem doing a default install (ie erase disk and install Ubuntu. No fancy resizing, selecting own partitions etc hence not duplicate of #1766945). But I did select LVM.
Repeated the installation but this time I first ensured I was connected to the internet with a wifi connection and then allowed downloading of updates during the installation. Installation was successful.
Possible caveat: I am booting in insecure mode. Not sure whether that makes a difference.