You can get a "legacy" installer for Focal server: http://cdimage.ubuntu.com/ubuntu-legacy-server/releases/20.04/release/ http://cdimage.ubuntu.com/ubuntu-lega

You can get a "legacy" installer for Focal server: http://cdimage.ubuntu.com/ubuntu-legacy-server/releases/20.04/release/ http://cdimage.ubuntu.com/ubuntu-legacy-server/releases/20.0... I'm using it myself for $DAYJOB, although, as you say, my Bionic preseed needed a _lot_ of adaptation.