virt-manager (or GNOME Boxes) instead of directly using the
qemu -kvm command. You will hopefully find that 1) the creation wizard attempts to autodetect the distribution & version of the install media; 2) if it fails to auto-detect, you will be offered a list which includes recent versions of Ubuntu. (I.e., if your Ubuntu version is too new to be listed in your virt-manager, you can usually just select the most recent Ubuntu version from the list. But see NOTE below in any case).
The implication is that
virt-manager chooses an efficient "hardware" configuration, which meets the hardware requirements of Ubuntu, and provides the most efficient virtual hardware that Ubuntu is able to use.
virt-manager also offers an option to expand this configuration, i.e. customize the hardware config before starting the install. Personally, I make sure to do this and and double-check the RAM size against the Ubuntu installation documents. I had to increase RAM size at one point to avoid the VM grinding to a halt somewhere during the install, I think this was with Ubuntu 18.04 but I might be mis-remembering.
I have successfully installed Ubuntu Desktop 16.04
and 18.04[*] from their respective live cds, using this method. (I think they do not default to LVM, but I tend to avoid enabling LVM inside VMs. Some of the uses of LVM may be met by instead creating and resizing separate virtual disks).
(If either Ubuntu enabled LVM by default for you, or you have a specific reason for wanting LVM services inside a VM, perhaps you could edit your question to be more specific).
[*] um. actually I forgot, something did go wrong with installing Ubuntu Destop 18.04 from the live cd, running inside virt-manager on Fedora Linux 28. The installer GUI stopped updating, and I think there was a kernel hung task message about QXL. Changing the type of virtual graphics hardware avoided this, I think I used Cirrus. It might be possible to change the graphics hardware back after finishing the install and applying all software updates including the kernel.