Ubuntu 22.04 and 24.04 wake up immediately (fixed)

Yesterday, I installed a clean installation of Ubuntu 24.04. At first, the sleep feature seemed to work properly. Then I installed some packages (both snap and deb packages). Today, I noticed that Ubuntu wakes up immediately when suspending. I had the same issue also on Ubuntu 22.04.

I have disabled all devices that can wake up the system using the method described here: Ubuntu wakes up after few seconds of sleep

So now the output of cat /proc/acpi/wakeup is:

Device  S-state   Status   Sysfs nodePS2K      S3    *disabledPS2M      S3    *disabledIP2P      S3    *disabledRP01      S4    *disabled  pci:0000:00:1c.0RP02      S4    *disabled  pci:0000:00:1c.1RP03      S4    *disabledRP04      S4    *disabled  pci:0000:00:1c.3RP06      S4    *disabledRP07      S4    *disabledRP08      S4    *disabledBR1B      S4    *disabled  pci:0000:00:01.1BR2A      S4    *disabled  pci:0000:00:02.0BR2B      S4    *disabledBR2C      S4    *disabledBR2D      S4    *disabledBR3A      S4    *disabled  pci:0000:00:03.0BR3B      S4    *disabled  pci:0000:00:03.1BR3C      S4    *disabled  pci:0000:00:03.2BR3D      S4    *disabled  pci:0000:00:03.3RP05      S4    *disabledLAN0      S4    *disabled  pci:0000:00:19.0BR1A      S4    *disabled  pci:0000:00:01.0EHC1      S0    *disabled  pci:0000:00:1d.0EHC2      S0    *disabled  pci:0000:00:1a.0XHCI      S0    *disabled  pci:0000:00:14.0QRP0      S4    *disabledQR1A      S4    *disabledQR1B      S4    *disabledQR2A      S4    *disabledQR2B      S4    *disabledQR2C      S4    *disabledQR2D      S4    *disabledQR3A      S4    *disabledQR3B      S4    *disabledQR3C      S4    *disabledQR3D      S4    *disabledRRP0      S4    *disabledRR1A      S4    *disabledRR1B      S4    *disabledRR2A      S4    *disabledRR2B      S4    *disabledRR2C      S4    *disabledRR2D      S4    *disabledRR3A      S4    *disabledRR3B      S4    *disabledRR3C      S4    *disabledRR3D      S4    *disabledSRP0      S4    *disabledSR1A      S4    *disabledSR1B      S4    *disabledSR2A      S4    *disabledSR2B      S4    *disabledSR2C      S4    *disabledSR2D      S4    *disabledSR3A      S4    *disabledSR3B      S4    *disabledSR3C      S4    *disabledSR3D      S4    *disabled

But the problem persists!

The issue may be related to NetworkManager, because just after a wake up, journalctl | grep -i "wake requested" gives

May 16 11:42:41 kant NetworkManager[1648]: <info>  [1715847161.6790] manager: sleep: wake requested (sleeping: yes  enabled: yes)

where the time matches with the time of the wake up.

Update 4 (FIX):

I replaced the keyboard with an old PS/2 keyboard I had and this fixed the problem. It's strange, because the previous keyboard worked properly otherwise.

Update 3:

I killed all processes appearing in the output of systemd-inhibit --list except GNOME Shell. One of them was NetworkManager. It didn't solve the problem. journalctl | grep -i "wake requested" doesn't show any new message.

Update 2:

Somebody suggested that I add the following lines to /etc/NetworkManager/NetworkManager.conf

[main]sleep-wake=false

and then invoke sudo systemctl restart NetworkManager

It wasn't helpful either. And, again, journalctl | grep -i "wake requested" produces

May 16 13:34:05 kant NetworkManager[12491]: <info>  [1715853845.6895] manager: sleep: wake requested (sleeping: yes  enabled: yes)

with the time matching the time of wake up.

Update 1:

Based on some information I found on the web, I tried to disable the wake-on-lan feature of network interfaces with sudo ethtool -s INTERFACE_NAME wol d, but it hasn't been helpful.