How do I get my laptop to wakeup only by power button with delay on Liquorix kernel?

Lubuntu 4.15.0-55-generic on Dell Venue can be easily configured to wakeup only by power button. And it should be pressed during 4 s. This prevents sudden wakeups in a bag.

After upgrading to 5.2.0-8.2-liquorix-amd64, the tablet wakes up immediately by any of three buttons: power, volume up and volume down. Sudden wakeups now occur at careless handling of the bag. But cat /proc/acpi/wakeup returns only PBTN as enabled device:

$ cat /proc/acpi/wakeup
Device  S-state   Status   Sysfs node
UAR1      S3    *disabled
RP01      S4    *disabled
PXSX      S4    *disabled
RP02      S4    *disabled
PXSX      S4    *disabled
RP03      S4    *disabled  pci:0000:00:1c.0
PXSX      S4    *disabled  pci:0000:01:00.0
RP04      S4    *disabled  pci:0000:00:1c.3
PXSX      S4    *disabled  pci:0000:02:00.0
RP05      S4    *disabled
PXSX      S4    *disabled
RP06      S4    *disabled
PXSX      S4    *disabled
RP07      S4    *disabled
PXSX      S4    *disabled
RP08      S4    *disabled
PXSX      S4    *disabled
GLAN      S4    *disabled
EHC1      S0    *disabled
EHC2      S0    *disabled
XHC   S0    *disabled  pci:0000:00:14.0
HDEF      S4    *disabled  pci:0000:00:1b.0
TPD4      S4    *disabled
PEG0      S4    *disabled
PEGP      S4    *disabled
PEG1      S4    *disabled
PEG2      S4    *disabled
LID0      S3    *disabled  platform:PNP0C0D:00
PBTN      S3    *enabled   platform:PNP0C0C:00

Is it possible to avoid waking up by volume buttons? Or is it possible to wake up when the power button (as a last resort, any of three buttons) is pressed for some time?