[SOLVED]: Yarn Debian Key Expiry Date Updated

 Solved by re-installing:

 curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -  
 echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list  
 sudo apt update  
 sudo apt install yarn  

Ref: https://linuxize.com/post/how-to-install-yarn-on-ubuntu-20-04/

[SOLVED] - Install phpMyAdmin & LAMP on Ubuntu 20.04 Desktop

Install phpMyAdmin & Linux, Apache, MySQL/MariaDB & PHP [LAMP] on Ubuntu 20.04 desktop.

Below you will find the instructions that I myself have tried and successfully implemented on my system.

 1. Install Apache Web Server

 sudo apt update  
 sudo apt install apache2  

2. Install MariaDB

 sudo apt install mariadb-server  
 sudo apt install mariadb-client  

After that, run the commands below to secure the MariaDB server by creating a root password, disallowing remote root access removing anonymous, and more.

 sudo mysql_secure_installation  

 If you've just installed MariaDB, and haven't set the root password yet, you should just press enter here.  
 Enter current password for root (enter for none): PRESS ENTER  
 Switch to unix_socket authentication [Y/n] n  
 Change the root password? [Y/n] n  
 Remove anonymous users? [Y/n] y  
 Disallow root login remotely? [Y/n] y  
 Remove test database and access to it? [Y/n] y  
 Reload privilege tables now? [Y/n] y  
 All done!  

3. Install PHP

 sudo apt install php7.4 php7.4-common php7.4-mysql php7.4-gmp php7.4-curl php7.4-intl php7.4-mbstring php7.4-xmlrpc php7.4-gd php7.4-xml php7.4-cli php7.4-zip  

4. Install phpMyAdmin

 sudo apt install phpmyadmin  

When prompted to choose the web server, select apache2 and continue.

   

When prompted again to allow web config-common to install a database and configure select Yes and press ENTER.

Then type and confirm a password.

After installing phpMyAdmin, open your web browser and browse to the server hostname or IP address followed by /phpmyadmin.

 http://localhost/phpmyadmin  

If you encounter the following error implement the solution below to resolve the issue:

ERROR: mysqli_real_connect(): (HY000/1698): Access denied for user 'root'@'localhost'

Open your terminal and run the following commands:

 sudo mysql -u root  

 use mysql;  
 update user set plugin='' where User='root';  
 flush privileges;  
 \q  

Now the LAMP cum phpMyAdmin should be working for you.

>> Ref:

1. https://geekrewind.com/how-to-install-phpmyadmin-on-ubuntu-linux-with-apache
2. https://stackoverflow.com/a/45142195/7206497