Boot method: debian-12.5.0-amd64-netinst.iso installation with attached USB-serial adapter
Image version:https://www.debian.org/releases/bookworm/debian-installer/debian-12.5.0-amd64-netinst.iso
Date: May 14th 2024

Machine: qemu-kvm 1:4.2-3ubuntu6.23 virtual machine
Processor: pass-through of four AMD Ryzen 7 PRO 2700 cores
Memory: 2 GB VM memory
Partitions: N/A

Output of lspci -knn (or lspci -nn) (tmpfs):
00:00.0 Host bridge [0600]: Intel Corporation 440FX - 82441FX PMC [Natoma] [8086:1237] (rev 02)
	Subsystem: Red Hat, Inc. Qemu virtual machine [1af4:1100]
00:01.0 ISA bridge [0601]: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II] [8086:7000]
	Subsystem: Red Hat, Inc. Qemu virtual machine [1af4:1100]
00:01.1 IDE interface [0101]: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II] [8086:7010]
	Subsystem: Red Hat, Inc. Qemu virtual machine [1af4:1100]
	Kernel driver in use: ata_piix
	Kernel modules: ata_piix, ata_generic
00:01.3 Bridge [0680]: Intel Corporation 82371AB/EB/MB PIIX4 ACPI [8086:7113] (rev 03)
	Subsystem: Red Hat, Inc. Qemu virtual machine [1af4:1100]
00:02.0 VGA compatible controller [0300]: Red Hat, Inc. Virtio GPU [1af4:1050] (rev 01)
	Subsystem: Red Hat, Inc. Device [1af4:1100]
	Kernel driver in use: virtio-pci
	Kernel modules: virtio_pci
00:03.0 Ethernet controller [0200]: Intel Corporation 82540EM Gigabit Ethernet Controller [8086:100e] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
00:04.0 Audio device [0403]: Intel Corporation 82801FB/FBM/FR/FW/FRW (ICH6 Family) High Definition Audio Controller [8086:2668] (rev 01)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel
00:05.0 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 [8086:2934] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: uhci_hcd
	Kernel modules: uhci_hcd
00:05.1 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 [8086:2935] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: uhci_hcd
	Kernel modules: uhci_hcd
00:05.2 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 [8086:2936] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: uhci_hcd
	Kernel modules: uhci_hcd
00:05.7 USB controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 [8086:293a] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: ehci-pci
	Kernel modules: ehci_pci
00:06.0 Communication controller [0780]: Red Hat, Inc. Virtio console [1af4:1003]
	Subsystem: Red Hat, Inc. Device [1af4:0003]
	Kernel driver in use: virtio-pci
	Kernel modules: virtio_pci
00:07.0 SATA controller [0106]: Intel Corporation 82801IR/IO/IH (ICH9R/DO/DH) 6 port SATA Controller [AHCI mode] [8086:2922] (rev 02)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]
	Kernel driver in use: ahci
	Kernel modules: ahci
00:08.0 Unclassified device [00ff]: Red Hat, Inc. Virtio memory balloon [1af4:1002]
	Subsystem: Red Hat, Inc. Device [1af4:0005]
	Kernel driver in use: virtio-pci
	Kernel modules: virtio_pci
00:09.0 Ethernet controller [0200]: Intel Corporation 82540EM Gigabit Ethernet Controller [8086:100e] (rev 03)
	Subsystem: Red Hat, Inc. QEMU Virtual Machine [1af4:1100]

Base System Installation Checklist:
[O] = OK, [E] = Error (please elaborate below), [ ] = didn't try it

Initial boot:           [O]
Detect network card:    [O]
Configure network:      [O]
Detect media:           [O]
Load installer modules: [E]
Detect hard drives:     [O]
Partition hard drives:  [O]
Install base system:    [O]
Clock/timezone setup:   [O]
User/password setup:    [O]
Install tasks:          [O]
Install boot loader:    [O]
Overall install:        [O]

Comments/Problems:

The issue happens when a custom USB-serial adapter with an internal FTDI chip
(module ftdi_sio) is plugged into the PC at the time the Debian installer frontend is initialized.
This seems to happen right after the syslog line
in syslog.txt which copied from the tmpfs installation system to the target system at the point
in time at which the first installer mask appears (language selection).

If a USB-serial adapter is given the Debian installer deactivates the graphic frontend and falls back to the text frontend
presumably as a serial console is detected (?). This is an issue for my company where customers are allowed to
reinstall the product PC using a preseeded Debian ISO which is always connected to an internal USB-serial adapter.

The issue is reproducible on a physical PC but also in a virtual machine (here KVM) where a physical
USB2-serial adapter was passed through to the VM (see VM configuration in attached pictures). The adapter does not
need any attached RS232 serial cable for the reproduction of the bug. As indicated it is easily reproducible
using a current Debian Bookworm ISO.

The issue was not reproducible under Debian Buster where the graphic frontend starts up as usual despite a
USB-serial adapter being present and was immediately observed after we switched from Buster to Bookworm.

Maybe the braille package brltty-udeb is involved here which appears prominently in the syslog.

I tried "modprobe.blacklist=ftdi_sio" as a Kernel parameter via grub and tried to set a "DEBIAN_FRONTEND=gtk" environment variable
but the text mode was still being used. The Kernel parameter "console=null" first kept the graphic mode as desired but then stops with
"no installation media found" so these options did not succeed.

Also I found a similar forum post here without a solution however:
https://forums.debian.net/viewtopic.php?t=157650

With best regards,
Christian