BUG #18199: 'Release' file not available in apt.postgresql.org/pub/repos/apt bionic-pgdg

The following bug has been logged on the website:

Bug reference: 18199
Logged by: Andrey Lizenko
Email address: lizenko79(at)gmail(dot)com
PostgreSQL version: 13.13
Operating system: Ubuntu 18.04.6 LTS
Description:

Trying to setup postgres according to this official instruction:

sudo sh -c 'echo "deb https://apt.postgresql.org/pub/repos/apt $(lsb_release
-cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list'
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo
apt-key add -
sudo apt-get update
sudo apt-get -y install postgresql

Here are two errors:

Err:5 https://apt.postgresql.org/pub/repos/apt bionic-pgdg Release
404 Not Found [IP: 87.238.57.227 443]

Reading package lists... Done
E: The repository 'https://apt.postgresql.org/pub/repos/apt bionic-pgdg
Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore
disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration
details.

Does it mean, that Ubuntu 18.04 LTS is no longer supported?

The previous steps were OK:

root(at)dm:~# sudo sh -c 'echo "deb https://apt.postgresql.org/pub/repos/apt
$(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list'
root(at)dm:~# wget --quiet -O -
https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
OK