How to setup LIRC on Ubuntu for Raspberry Pi?

I installed Ubuntu Server 20.04.2 LTS for Raspberry Pi on my Raspberry Pi 3 B+.

$ uname -a
Linux ubuntu 5.4.0-1042-raspi #46-Ubuntu SMP PREEMPT Fri Jul 30 00:35:40 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS
Release:        20.04
Codename:       focal

I installed LIRC and tried following this guide. My goal is to be able to receive infrared remote control commands.

My /etc/lirc/lirc_options.conf file:

[lircd]
nodaemon        = False
driver          = default
device          = /dev/lirc0
output          = /var/run/lirc/lircd
pidfile         = /var/run/lirc/lircd.pid
plugindir       = /usr/lib/aarch64-linux-gnu/lirc/plugins
permission      = 666
allow-simulate  = No
repeat-max      = 600

However, there is no /boot/config.txt file (I mean obviously, because that is specific to Raspberry Pi OS), so I cannot tell LIRC which GPIO pin to use as the guide states:

dtoverlay=gpio-ir,gpio_pin=17

I tried rebooting anyway and then, as the guide suggests:

$ sudo systemctl stop lircd.service
Warning: Stopping lircd.service, but it can still be activated by:
  lircd.socket
$ sudo systemctl stop lircd.socket
$ sudo mode2 -d /dev/lirc0
Using driver default on device /dev/lirc0
Cannot initiate device /dev/lirc0

The /dev/lirc0 device is not even mounted, ls /dev | grep lirc no results. Is there anything I can do to get it working? I cannot figure out what to do and cannot find any recent guides.

Extra info:

• I'm using TSOP4838 IR receiver on GPIO 17
• I was able to read raw data from this receiver using GPIO. The pin is correctly High and receives Low only when I press the remote control buttons. I think I need LIRC for hardware support as it is not reliable to implement the remote control IR protocol using a Python script (or is it?) as you need to read at perfect time intervals. That is a job for a low-level library or a hardware CLK and the like.
• Bonus question: The remote control is LG AKB73655802 is there a configuration for LIRC for this specific remote control, or do I need to make my own?

I had a similar problem today, switching the OS of my Raspberry from Raspbian to Ubuntu Server. Searching for the solution of this problem, I came across this post: https://forums.raspberrypi.com/viewtopic.php?t=302355

and adapting this to my setup, the following worked:

sudo vim /boot/firmware/usercfg.txt

and insert:

#output
dtoverlay=gpio-ir-tx,gpio_pin=24
#input
dtoverlay=gpio-ir,gpio_pin=23