Step-by-step – Arduino IDE Installation in Ubuntu 20.04 Guide

Installing

2. 2. Setting Up Flatpak

   How to Setup Flatpak on Ubuntu 20.04

   Flatpak Ubuntu 20.04 Installation Guide

   Flatpak Ubuntu 20.04 Setup

3. 3. Installing Arduino IDE

   Then to Install Arduino IDE Flatpak App on Ubuntu 20.04
   Simply play:

   flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

   For further Insight see the Flatpak Official Documentation.
   And after:

   flatpak install https://flathub.org/repo/appstream/cc.arduino.arduinoide.flatpakref

   The Flatpak App Setup do Not need the sudo Command because then it Runs confined into a Sandbox.
   However, you’ll be Prompted to Authenticate with your User or Admin Pass.
   Then Confirm the proposed Setup with ‘Enter’ and wait until the App is Downloaded and Installed.