Fresh Neon install can't boot if encryption is used (20240201-0717 iso)

After the Neon updater hosed my system (as documented here: Upgrade to 22.04 breaks Neon, can't boot), I wiped the partition and attempted a whole fresh reinstall. However, the installer doesn’t seem to work properly if full disk encryption is used. Repro:

  1. Download the ISO (20240201-0717), copy to USB & boot live
  2. Once booted, connect to wifi & launch the installer
  3. On the Partitions step, choose “Manual Partitioning”:
    • Select free space->Create. File System=btrfs, Encrypt=checked, Mount Point=/
    • As it’s a multi-boot system, I have an existing fat32 efi partition. Select that partition->Edit. Set its mount point to /boot/efi.
  4. Proceed with the install
  5. Reboot.

Result: It prompts for the password, accepts the password, shows the Grub menu, I select Neon, then it fails to boot. The error is cryptsetup: ERROR luks-(uuid): maximum number of tries exceeded. If I hit a key to show the text, it reveals:

/bin/cat: /crypto_keyfile.bin: No such file or directory
Nothing to read on input.
cryptsetup: ERROR: luks-(uuid): cryptsetup failed, bad password or options?
(...repeating over and over until it gives up & drops to shell)
  • This was the exact install process that worked properly with the previous version of Neon (20.04). Just to sanity check my steps, I went back & fully reinstalled the 20220324-0945 ISO. It worked without issue. So this definitely seems to be a regression.
  • After some googling, I found threads that say the current installer is broken only with encryption & btrfs, so I tried to repeat the process using ext4 rather than btrfs. The same error occurred.
  • I also tried choosing “Replace a partition” rather than “Manual Partitioning.” I gave it the partition I intended to use as “/” (aka I didn’t explicitly give it /boot/efi). Same issue.
  • I tried doing the same, but not selecting encryption (not an option for real-world use, but just out of curiosity). That worked.

So it seems to be unable to install with encryption.

Further googling turned this up, with others reporting the same: https://www.reddit.com/r/kdeneon/comments/1aenouy/kde_neon_wont_boot_after_fresh_install_cryptsetup/?rdt=37809

I’ve tried all the suggested steps on that reddit, but can’t seem to get a fresh install working. Any help would be appreciated, as I’m hoping after a full day lost, I won’t be stuck just having to reinstall the same old 20.04 version I’d been using prior to trying to upgrade.