a) This hasn't ceased to work for your desktop - you can continue to do this through the upgrade cycle, as it would only affect new installs (safely converting native fs to dmcrypt isn't possible, AFAIK)
b) during an installation you could eschew FDE and opt for a PV, as I do, that you put your selected, secure LV's onto. I use Debian in preference to Ubuntu, but I'm sure they're materially identical in this case -- two physical partitions -- /boot and not-boot. /boot isn't encrypted in my case, but /, and /home (and a couple of others, though not swap of course) are LVM2 volumes sitting on top of the encrypted 'rest of the disk' partition. If you have /home only with noauto option in fstab , pointing to a an LV on the crypted partition, you could continue to do what you're doing, with the same reduced security confidence.