Need to see the console boot messages, not the splash screen

Question

I am running Ubuntu 21.04 on RPi 4. On boot up, I would like to see the console boot messages in real time (and not the splash screen).

On Intel PCs, that's easily done by editing the grub2 config files.

On RPi, there is no Grub. How can I do it on my installation?

Note, that the usual ways of doing it for the Raspberry Pi Linux distributions, do not work in Ubuntu.

~$ lsb_release -a
   Distributor ID:  Ubuntu;  Description:   Ubuntu 21.04;  Release: 21.04;  Codename:   hirsute
~$ uname -a
   Linux 5.11.0-1015-raspi #16-Ubuntu SMP PREEMPT aarch64 aarch64 aarch64 GNU/Linux

Update #1

/boot/cmdline.txt does not exist:

~$ ls -l /boot
total 80163
config-5.11.0-1007-raspi
config-5.11.0-1015-raspi
dtb -> dtbs/5.11.0-1015-raspi/./bcm2711-rpi-4-b.dtb
dtb-5.11.0-1007-raspi -> dtbs/5.11.0-1007-raspi/./bcm2711-rpi-4-b.dtb
dtb-5.11.0-1015-raspi -> dtbs/5.11.0-1015-raspi/./bcm2711-rpi-4-b.dtb
dtbs
1969 firmware
grub
initrd.img -> initrd.img-5.11.0-1015-raspi
initrd.img-5.11.0-1007-raspi
initrd.img-5.11.0-1015-raspi
initrd.img.old -> initrd.img-5.11.0-1007-raspi
System.map-5.11.0-1007-raspi
System.map-5.11.0-1015-raspi
vmlinuz -> vmlinuz-5.11.0-1015-raspi
vmlinuz-5.11.0-1007-raspi
vmlinuz-5.11.0-1015-raspi
vmlinuz.old -> vmlinuz-5.11.0-1007-raspi

~$ ls -l /boot/grub
total 2344
grubenv
unicode.pf2

/proc/cmdline does not exist, either.

Is there a way to do it with "plymouth"?

Maybe the way to do it is to edit this part of: /boot/config-5.11.0-1015-raspi ?

#
# printk and dmesg options
#
CONFIG_PRINTK_TIME=y
# CONFIG_PRINTK_CALLER is not set
CONFIG_CONSOLE_LOGLEVEL_DEFAULT=7
CONFIG_CONSOLE_LOGLEVEL_QUIET=4
CONFIG_MESSAGE_LOGLEVEL_DEFAULT=4

Answer 1

I found it.

cmdline.txt is found in /boot/firmware .