Установите PHP 7.x на Ubuntu 16.04

Очевидно, мне не разрешено задавать этот вопрос о stackoverflow , поэтому я просто сделаю это здесь.

Я знаю, что этот вопрос задавали много, но меня всегда приводили к одному и тому же ответу, который не решает мою проблему.

Обычно предлагается следующее решение:

~$ sudo apt-get install software-properties-common python-software-properties;
~$ sudo add-apt-repository -y ppa:ondrej/php;
~$ sudo apt-get update;

И готово! Но, к сожалению, не в моем случае.

Итак, после выполнения ранее упомянутых шагов, я пытаюсь установить «любую» версию PHP 7.x через apt , но, похоже, пакеты для любой версии PHP не могут быть найдены.

~$ sudo apt install php7.4;
Reading package lists... Done
Building dependency tree... 50%
Building dependency tree       
Reading state information... Done
Note, selecting 'php7.4-gd' for regex 'php7.4'
Note, selecting 'php7.4-cli' for regex 'php7.4'
Note, selecting 'php7.4-dom' for regex 'php7.4'
Note, selecting 'php7.4-ffi' for regex 'php7.4'
Note, selecting 'php7.4-ftp' for regex 'php7.4'
Note, selecting 'php7.4-xmlreader' for regex 'php7.4'
Note, selecting 'php7.4-mysqli' for regex 'php7.4'
Note, selecting 'php7.4-sysvmsg' for regex 'php7.4'
Note, selecting 'php7.4-json' for regex 'php7.4'
Note, selecting 'php7.4-phar' for regex 'php7.4'
Note, selecting 'php7.4-tokenizer' for regex 'php7.4'
Note, selecting 'php7.4-curl' for regex 'php7.4'
Note, selecting 'php7.4-shmop' for regex 'php7.4'
Note, selecting 'php7.4-pdo-mysql' for regex 'php7.4'
Note, selecting 'php7.4-sysvsem' for regex 'php7.4'
Note, selecting 'php7.4-sysvshm' for regex 'php7.4'
Note, selecting 'php7.4-pdo' for regex 'php7.4'
Note, selecting 'php7.4-sockets' for regex 'php7.4'
Note, selecting 'php7.4-ctype' for regex 'php7.4'
Note, selecting 'php7.4-calendar' for regex 'php7.4'
Note, selecting 'php7.4-intl' for regex 'php7.4'
Note, selecting 'php7.4-fileinfo' for regex 'php7.4'
Note, selecting 'php7.4-opcache' for regex 'php7.4'
Note, selecting 'php7.4-soap' for regex 'php7.4'
Note, selecting 'php7.4-xml' for regex 'php7.4'
Note, selecting 'php7.4-xsl' for regex 'php7.4'
Note, selecting 'php7.4-zip' for regex 'php7.4'
Note, selecting 'php7.4-simplexml' for regex 'php7.4'
Note, selecting 'php7.4-mysql' for regex 'php7.4'
Note, selecting 'php7.4-mbstring' for regex 'php7.4'
Note, selecting 'php7.4-readline' for regex 'php7.4'
Note, selecting 'php7.4-exif' for regex 'php7.4'
Note, selecting 'php7.4-mysqlnd' for regex 'php7.4'
Note, selecting 'php7.4-common' for regex 'php7.4'
Note, selecting 'php7.4-bcmath' for regex 'php7.4'
Note, selecting 'php7.4-posix' for regex 'php7.4'
Note, selecting 'php7.4-iconv' for regex 'php7.4'
Note, selecting 'libapache2-mod-php7.4' for regex 'php7.4'
Note, selecting 'php7.4-gettext' for regex 'php7.4'
Note, selecting 'php7.4-xmlwriter' for regex 'php7.4'
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

Что еще интересно, когда я использую apt search , действительно кажется, что нет пакета для какой-либо php версии

~$ sudo apt search php7.4
Sorting... Done
Full Text Search... Done
libapache2-mod-php7.4/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-bcmath/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-cli/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]

  (none)

php7.4-common/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-curl/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-gd/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-intl/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

php7.4-json/now 7.4.13-1+ubuntu16.04.1+deb.sury.org+1 amd64 [residual-config]
  (none)

... etc

Что мне не хватает?

Изменить: после выполнения apt-get purge php7.4 сообщение для (по крайней мере PHP 7.4) изменилось на следующее:

~$ sudo apt-get install -y php7.4
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package php7.4
E: Couldn't find any package by glob 'php7.4'
E: Couldn't find any package by regex 'php7.4'