Hey there, let's tackle this problem step by step — I totally get the frustration of needing to preserve existing partitions on your only drive for a home server. Here are some actionable solutions to get Ubuntu 22.04.4 Server installed without wiping your existing data/OS partitions:

• Double-check your installation ISO
  Make sure you downloaded the standard Ubuntu Server 22.04.4 LTS ISO (not a cloud-specific or optimized variant like for AWS/Azure). Those specialized builds often skip manual partition options to streamline cloud deployments.

• Look for "Custom storage layout" instead of "Manual"
  Ubuntu renamed the old "Manual" partition option to Custom storage layout in newer versions of the Subiquity installer (used for Server editions). When you reach the storage configuration screen:

  1. Don't select "Use an entire disk" — this will wipe your entire drive.
  2. Instead, pick "Custom storage layout" — this lets you:
     • View all existing partitions and mark them as Do not format to keep them intact.
     • Create new partitions in the free space at the end of your drive for Ubuntu's root (/), swap, and /boot (or EFI partition if using UEFI).
       This is exactly the same functionality as the old "Manual" option, just rebranded — it's easy to miss if you're looking for the old wording!

• Try switching BIOS/UEFI mode
  In rare cases, the installer menu might behave differently depending on whether you're booting in legacy BIOS or UEFI mode. If you don't see the custom layout option in one mode, switch to the other in your PC's BIOS settings before rebooting the installer.

• Manual installation via debootstrap (for advanced users)
  If the graphical installer still isn't cooperating, you can use the Server ISO's live mode to install Ubuntu manually from the command line:

  1. Boot the ISO and select "Try Ubuntu Server" (or the live command-line option).
  2. Identify your existing partitions and free space using commands like lsblk or fdisk -l.
  3. Create the necessary partitions in the free space, format them, and mount them to /mnt, /mnt/boot, etc.
  4. Run debootstrap jammy /mnt to install the base system, then chroot into /mnt to configure users, GRUB, and other system settings.
     This method is more hands-on, but gives you full control over every part of the partition setup.

If none of these methods work, switching to Debian 12 (which you already noted supports preserving existing partitions during installation) is a reliable backup plan. But the "Custom storage layout" option should be your first stop — it's almost certainly the renamed version of the "Manual" option you're familiar with.

备注：内容来源于stack exchange，提问作者TheStarman