ls: cannot access '/sys/firmware/efi': No such file or directory

I haven't changed anything yet... still using the 'puter for other stuff today.

Don't know. I wouldn't dare to guarantee anything. Anyhow, on one hand it should not hurt. Give it a try.

My advice: when you go and modify any setting in the bios or in your sw, take notes you can later refer to. Makes life easier in the long run.

Another thing I would try: reset this autologin to normal login with username/password until the blank screen is solved. Removes an additional variable.

 bash: UEFI: command not found 

I'll reset the bios to default I guess, then update grub. That would fix it, right?

Bios version: Your PC has an efi Bios dated from 2013. I would make sure that this really is the latest that is available for this PC. And if not upgrade it in any case.
Legacy or efi mode: looks like your PC is booting in legacy mode now. Fits to the last update as indicated in response #7. Do you recollect how you installed your PC? Which mode did you use?
Dual boot: And you say you are dual booting? Which is the second OS on the other HDD?

Please show a

# fdisk -l

Sources.list: I think line 2 is a cripped deb-src entry. In any case its partially duplicating line 1, so it superfluous, it overwrites line 1. My suggestion: delete lines 2, 4 and 6. I think you are not compiling and linux software on your PC, are you?

On my PC it works fine with copy/paste:

~$ [ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
UEFI

My PC is running in efi mode obviously. Do not try to type that line in, you are prone to mistakes, use copy/paste to a terminal. Works fine in a user terminal.

Again:

I still think this is true. There must be another reason for the problems.

Do you remember what exactly, which settings, you modified in the bios a few days ago?

Maybe its worth checking the bios battery. Maybe that is borderline?

inxi -Fzr

is:

 robin@devuan:~$ inxi -Fzr
System:
  Kernel: 6.12.86+deb13-amd64 arch: x86_64 bits: 64
  Desktop: Xfce v: 4.20.1 Distro: Devuan GNU/Linux 6 (excalibur)
Machine:
  Type: Desktop System: Dell product: OptiPlex 7010 v: 01
    serial: <superuser required>
  Mobo: Dell model: 0YXT71 v: A02 serial: <superuser required> BIOS: Dell
    v: A16 date: 09/09/2013
CPU:
  Info: quad core model: Intel Core i5-3570 bits: 64 type: MCP cache:
    L2: 1024 KiB
  Speed (MHz): avg: 3800 min/max: 1600/3800 cores: 1: 3800 2: 3800 3: 3800
    4: 3800
Graphics:
  Device-1: Intel Xeon E3-1200 v2/3rd Gen Core processor Graphics driver: i915
    v: kernel
  Display: unspecified server: X.org driver: X: loaded: modesetting
    unloaded: fbdev,vesa dri: crocus gpu: i915 resolution: 1920x1080~60Hz
  API: EGL v: 1.5 drivers: crocus,swrast
    platforms: gbm,x11,surfaceless,device
  API: OpenGL v: 4.5 compat-v: 4.2 vendor: intel mesa v: 25.2.6-1~bpo13+1
    renderer: Mesa Intel HD Graphics 2500 (IVB GT1)
  Info: Tools: api: eglinfo,glxinfo de: xfce4-display-settings x11: xdriinfo,
    xdpyinfo, xprop, xrandr
Audio:
  Device-1: Intel 7 Series/C216 Family High Definition Audio
    driver: snd_hda_intel
  Device-2: Logitech Headset H390 driver: hid-generic,snd-usb-audio,usbhid
    type: USB
  API: ALSA v: k6.12.86+deb13-amd64 status: kernel-api
Network:
  Device-1: Intel 82579LM Gigabit Network driver: e1000e
  IF: eth0 state: up speed: 1000 Mbps duplex: full mac: <filter>
Drives:
  Local Storage: total: 298.02 GiB used: 13.98 GiB (4.7%)
  ID-1: /dev/sda vendor: Seagate model: ST3160815AS size: 149.01 GiB
  ID-2: /dev/sdb vendor: Samsung model: HD161GJ size: 149.01 GiB
Partition:
  ID-1: / size: 145.61 GiB used: 13.98 GiB (9.6%) fs: ext4 dev: /dev/sda1
Swap:
  Alert: No swap data was found.
Sensors:
  System Temperatures: cpu: 44.0 C mobo: N/A
  Fan Speeds (rpm): N/A
Repos:
  Active apt repos in: /etc/apt/sources.list
    1: deb http://deb.devuan.org/merged/ excalibur main contrib non-free non-free-firmware
    2: deb http://deb.devuan.org/merged/ excalibur main non-free-firmware
    3: deb http://deb.devuan.org/merged/ excalibur-security main contrib non-free non-free-firmware
    4: deb-src http://deb.devuan.org/merged/ excalibur-security main contrib non-free non-free-firmware
    5: deb http://deb.devuan.org/merged/ excalibur-updates main contrib non-free non-free-firmware
    6: deb-src http://deb.devuan.org/merged/ excalibur-updates main contrib non-free non-free-firmware
    7: deb http://deb.devuan.org/merged/ excalibur-backports non-free-firmware non-free contrib main
  No active apt repos in: /etc/apt/sources.list.d/antix.list
  Active apt repos in: /etc/apt/sources.list.d/home:hawkeye116477:waterfox.list
    1: deb http://download.opensuse.org/repositories/home:/hawkeye116477:/waterfox/Debian_12/ /
  Active apt repos in: /etc/apt/sources.list.d/xlibre-debian.sources
    1: deb https://xlibre-debian.github.io/devuan/ main stable
Info:
  Memory: total: 8 GiB available: 7.65 GiB used: 1.81 GiB (23.6%)
  Processes: 212 Uptime: 19h 35m Shell: Bash inxi: 3.3.38
robin@devuan:~$ 

And out of

 [ -d /sys/firmware/efi ] && echo UEFI || echo BIOS 

is: nothing, no response from the terminal.

So I went into the BIOS and made sure Secure Boot was disabled, UEFI-only is enabled (it was Legacy when the trouble started). That was supposed to fix it but didn't...

Hi Robin, according what you just showed it looks like you switched your PC from efi mode to legacy mode at 2026-05-09 10:59:46. The update is a consequence of that.

greenjeans thought its the other way round.

In any case, looks like you played around in the bios without understanding what you did. As a matter of fact, in efi mode Secure Boot can be on (=often called Windows OS) or off (Other OS or similar). It is better to turn it off since there is no real benefit in having it enabled. In legacy mode with CSM on, SB is automagically disabled.

On the other hand, just switching from efi to legacy should not at all affect the graphics, except for whatever reason?

Maybe its a good idea to show us details about what we are talking about. Please show us the result from

inxi -Fzr

from prompt to prompt in code tags please. It is possible that you have too install inxi first of all.

And in addition, the result from

[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS 

 Start-Date: 2026-05-09  10:59:46
Requested-By: robin (1001)
Install: grub-pc:amd64 (2.12-9+deb13u1, automatic)
Remove: grub-efi-amd64:amd64 (2.12-9+deb13u1)
End-Date: 2026-05-09  11:00:53

I guess that's an update?

So I went into the BIOS and made sure Secure Boot was disabled, UEFI-only is enabled (it was Legacy when the trouble started).

Wait, so you installed the system as MBR with the Legacy/CSM turned on in BIOS and UEFI turned off, then went in after the fact (as part of trying to diagnose the issue) and switched UEFI on in BIOS without making any other changes? If so that's going to cause new issues....

- Look in /var/log/Xorg.0.log for lines with (EE) to see if there are any errors.

- Look in /var/log/apt/history.log to see if any graphics related packages got upgraded.

- Look in /etc/lightdm/lightdm.conf to see if the two autologin lines are uncommented and have the correct user name. Make sure you scroll down to the [Seat:*] section and not in the extensive comments section above.

- Before you run startx, log in as root and run service lightdm status. If it's not running, try starting it, and if it's running, try restarting it. service lightdm start or service lightdm stop && service lightdm start (I can never get 'restart' to work.)

I installed RefractaOS, Xfce, and installed it from the Live session, choosing auto-login at installation. It all worked just fine until yesterday when it started doing this. It effects everything, though, both OSes on both HDDs and even booting from a USB stick! So I went into the BIOS and made sure Secure Boot was disabled, UEFI-only is enabled (it was Legacy when the trouble started). That was supposed to fix it but didn't... I don't have Slim, but rather LightDM and all the config files in there are unchanged from installation.

I used to install from the live desktop, which booted to desktop, with sudo configured; nowadays, I just use the server version & install with XFCE, (no sudo configured).