I frequently install Ubuntu on VMs running under Proxmox or VMware. Every time the installer gets to curtin command in-target and stays there for at least half an hour, sometimes much longer. The Ubuntu installer at this point gives an option to "Cancel update and reboot", but if that is chosen it then sits unchanging for about the same time that just leaving it to complete does.
I'm in a major network data center with ten gigabit connectivity, so the problem isn't slow local networking. I can shortcut the issue by resetting the VM, and if I do so then once it boots I can then install all the updates in a fraction of the time using apt update and apt upgrade, however I'm wary of using tricks like that on what will be production systems.
I've tried Googling and searching here for anything explaining why this stage of the Ubuntu installer takes so long, but I haven't found anything specific, although I have found a recommendation to not have any NICs on the system while installing and only add them post-install as a way to speed things up.
What is this curtin command in-target stage of the Ubuntu installer, why does it take so long, and are there any drawbacks to just pressing the reset button and then using apt update and apt upgrade post-boot instead?