We deferred to switching to the new installer until 22.04 and kept using the legacy net boot image for as long as possible. The switchover wasn't as bad as I was afraid it would and took only a few days to make new internal app to drive our installations. The worst part of the new installer is it requires a minimum of 2GiB of RAM to run, so all of our new VMs have to start with at least that much and be scaled down later
Except for the giant, buggy change in the auto-install process in 20.04:
* https://utcc.utoronto.ca/~cks/space/blog/linux/Ubuntu2004Aut...