This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-install-arduino-ide-on-ubuntu-20-04-focal-fossa
Thanks for writing this post! There is a step missing, however. Before the user can upload firmware to a board, they need to execute
sudo usermod -a -G dialout $USER and restart their computer.
For more info, see the “setup” instructions in the store page: