Start from terminal without installing bootloader:

sudo --preserve-env=DBUS_SESSION_BUS_ADDRESS,XDG_DATA_DIRS,XDG_RUNTIME_DIR sh -c 'ubiquity -b -d'

Get more options

ubiquity --help

There is no obvious way to prevent the installer from reformatting swap space.

• https://forums.linuxmint.com/viewtopic.php?f=46&t=391307
• https://forums.linuxmint.com/viewtopic.php?p=2208218
• https://wiki.debian.org/DebianInstaller/Preseed#Preseeding_methods
• https://www.debian.org/releases/stable/i386/apb.en.html
• https://www.debian.org/releases/stable/example-preseed.txt
• https://forums.linuxmint.com/viewtopic.php?p=2213523
• https://community.linuxmint.com/idea/welcome
• https://forums.linuxmint.com/viewtopic.php?f=46&t=390229
• https://flugel.it/linux/preseed-notes-autopartition-with-lvm/
• https://serverfault.com/questions/893387/how-to-make-custom-partitioning-of-hdd-via-preseed
• https://github.com/nuada/ubuntu-preseed/blob/master/partitions-boot-root-swap.template
• https://askubuntu.com/questions/1028234/create-preseed-partitions
• https://github.com/bonddim/linux-unattended-installation/blob/master/ubuntu/preseed
• https://forums.linuxmint.com/viewtopic.php?t=392336
• https://forums.linuxmint.com/viewtopic.php?p=1956995
• https://www.linuxquestions.org/questions/linux-newbie-8/my-partman-auto-expert_recipe-section-is-being-ignored-by-preseed-with-debian-4175717267/
• https://github.com/xobs/debian-installer/blob/master/doc/devel/partman-auto-recipe.txt