Unable to locate package php8.3 [duplicate]

I am trying to upgrade from PHP 7.2 to PHP 8.3 on a Ubuntu 18.04.6 LTS server. I am following so many tutorials that indicate the same steps:

sudo add-apt-repository ppa:ondrej/phpsudo apt updatesudo apt install php8.3

But this does not work. I get this message:

Reading package lists... DoneBuilding dependency treeReading state information... DoneE: Unable to locate package php8.3E: Couldn't find any package by glob 'php8.3'E: Couldn't find any package by regex 'php8.3'

And when I ran the update, I saw these messages that I guess could be related:

Ign:5 https://packages.sury.org/php bionic InReleaseErr:6 https://packages.sury.org/php bionic Release  404  Not Found [IP: 212.102.46.118 443]E: The repository 'https://packages.sury.org/php bionic Release' does not have 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.

How could I fix it?