Download latest IDE tarball from the Arduino store, unpack the tar file and install bin symlink, desktop files and add menu entries.

Some (most) Arduino sketches will require access to the python2 pyserial library [1]. Unfortunately there is no stock package for this in Ubuntu 20.04. Below is an alternative set of instructions to make pyserial available:

sudo apt install python2
python2 --version
curl https://bootstrap.pypa.io/pip/2.7/get-pip.py --output get-pip.py
sudo python2 get-pip.py
pip2 install pyserial

Make sure that the xdg-utils package is installed (this is only required if using the install script below):

sudo apt install xdg-utils

We are now ready to install the Arduino framework:

cd ~/Downloads
wget https://www.arduino.cc/download_handler.php?f=/arduino-1.8.13-linux64.tar.xz
cd /opt
sudo tar xvf ~laczik/Downloads/arduino-1.8.13-linux64.tar.xz
sudo chown -R root.root arduino-1.8.13/

If only a symlink is needed in /usr/local/bin

sudo ln -s /opt/arduino-1.8.13/arduino /usr/local/bin/

otherwise, if you also want to install desktop links, menu items and icons

sudo /opt/arduino-1.8.13/install.sh

Additional information:
Arduino Quick start guide and Getting started guide.

[1] An example of this is the software framework used with the ESP32 and ESP8266 modules, which generate up ‘ImportError: No module named serial’ error messages. Further information:
– Arduino IDE for the ESP32 / ESP8266 modules
– Installing and using pip