Kernels from vanilla:mainline-wo-mergew copr hang after UEFI boot menu selection

I’ve been using the vanilla:mainline-wo-mergew copr since F37 as suggested by other pkg maintainer for my help troubleshooting. I’ve been pretty happy with it, but after upgrading to F39, it hasn’t been booting correctly. When I install a new kernel with dnf upgrade or GNOME Software, it sometimes works on the first reboot, but all subsequent reboots hang very early after kernel selection at the UEFI boot menu, or if I don’t use the boot menu and it tries the default entry. The kernel from F39 updates repo works fine, though.

I don’t understand for several reasons. First of all, I came from GRUB, and I still don’t totally understand EFI. Secondly, it was working before, and I don’t understand why it would just stop. Third, I see the initrd files in the /efi partition, but the files for kernel 6.6-13-200 (current F39) and the mainline-wo-mergew kernel look the same to me. It feels like it’s hanging not able to find initrd, but both the working kernel and the not-working kernel both have valid initrd files in the respective locations and the conf files in /efi/loader/entries/* point to them.

$ sudo -i bootctl
      Firmware: UEFI 2.70 (American Megatrends 5.17)
 Firmware Arch: x64
   Secure Boot: disabled (setup)
  TPM2 Support: yes
  Boot into FW: supported

Current Boot Loader:
      Product: systemd-boot 254.8-2.fc39
     Features: ✓ Boot counting
               ✓ Menu timeout control
               ✓ One-shot menu timeout control
               ✓ Default entry control
               ✓ One-shot entry control
               ✓ Support for XBOOTLDR partition
               ✓ Support for passing random seed to OS
               ✓ Load drop-in drivers
               ✓ Support Type #1 sort-key field
               ✓ Support @saved pseudo-entry
               ✓ Support Type #1 devicetree field
               ✓ Enroll SecureBoot keys
               ✓ Retain SHIM protocols
               ✓ Boot loader sets ESP information
          ESP: /dev/disk/by-partuuid/e8ed8064-31cb-475d-adf0-b3a7e0d2517e
         File: └─/EFI/BOOT/BOOTX64.EFI

Random Seed:
 System Token: set
       Exists: yes

Available Boot Loaders on ESP:
          ESP: /efi (/dev/disk/by-partuuid/e8ed8064-31cb-475d-adf0-b3a7e0d2517e)
         File: ├─/EFI/systemd/systemd-bootx64.efi (systemd-boot 254.8-2.fc39)
               └─/EFI/BOOT/BOOTX64.EFI (systemd-boot 254.8-2.fc39)

Boot Loaders Listed in EFI Variables:
        Title: UEFI OS
           ID: 0x0001
       Status: active, boot-order
    Partition: /dev/disk/by-partuuid/e8ed8064-31cb-475d-adf0-b3a7e0d2517e
         File: └─/EFI/BOOT/BOOTX64.EFI

        Title: Linux Boot Manager
           ID: 0x0000
       Status: active, boot-order
    Partition: /dev/disk/by-partuuid/e8ed8064-31cb-475d-adf0-b3a7e0d2517e
         File: └─/EFI/systemd/systemd-bootx64.efi

Boot Loader Entries:
        $BOOT: /efi (/dev/disk/by-partuuid/e8ed8064-31cb-475d-adf0-b3a7e0d2517e)
        token: f723337b53e54d03907ea57c18c2c125

Default Boot Loader Entry:
         type: Boot Loader Specification Type #1 (.conf)
        title: Fedora Linux 39 (Workstation Edition) (6.8.0-0.rc3.225.vanilla.fc39.x86_64)
           id: f723337b53e54d03907ea57c18c2c125-6.8.0-0.rc3.225.vanilla.fc39.x86_64.conf
       source: /efi//loader/entries/f723337b53e54d03907ea57c18c2c125-6.8.0-0.rc3.225.vanilla.fc39.x8>
     sort-key: fedora
      version: 6.8.0-0.rc3.225.vanilla.fc39.x86_64
   machine-id: f723337b53e54d03907ea57c18c2c125
        linux: /efi//f723337b53e54d03907ea57c18c2c125/6.8.0-0.rc3.225.vanilla.fc39.x86_64/linux
       initrd: /efi//f723337b53e54d03907ea57c18c2c125/6.8.0-0.rc3.225.vanilla.fc39.x86_64/initrd
      options: root=/dev/mapper/vgNew-LVroot ro rhgb rd.luks.uuid=luk>
$ sudo -i efibootmgr 
BootCurrent: 0001
Timeout: 1 seconds
BootOrder: 0001,0000
Boot0000* Linux Boot Manager	HD(3,GPT,e8ed8064-31cb-475d-adf0-b3a7e0d2517e,0x114000,0x113000)/\EFI\systemd\systemd-bootx64.efi
Boot0001* UEFI OS	HD(3,GPT,e8ed8064-31cb-475d-adf0-b3a7e0d2517e,0x114000,0x113000)/\EFI\BOOT\BOOTX64.EFI0000424f

Naturally, I’ve had good luck booting after the kernel update I did immediately after posting. Perhaps, when it happens again, I can compare bootctl output to this record and see something that has changed. More later.

In the mean time, if anyone sees something I’m missing with the above, please let me know.