MULTIVERSIONS ON UBUNTU BOX

sudo apt install apache2 libapache2-mod-fastcgi

sudo apt-get install mysql-server
sudo mysql_secure_installation


sudo apt install software-properties-common
sudo add-apt-repository ppa:ondrej/php
sudo apt update

Use this command to install different versions of php just changing the string 7.1 to the required version
sudo apt install php7.1 php7.1-fpm libapache2-mod-php7.1


NOW ALL SET LAMP is installed and working


Now while u will require to change the php version

This command will change the php version on system
sudo update-alternatives --config php


Disable all version apached modules of php installed, just replace the 7.4 in below command
sudo a2dismod php7.4

Enable the version u need to use with apache, just replace the 8.0 in below command
sudo a2enmod php8.0

Restart the apache
sudo service apache2 restart