This page leads you to upgrade Ubuntu system to the latest version.

sudo apt update
sudo apt full-upgrade
sudo do-fenix-full-upgrade
sync
sudo reboot

If you encounter the following errors:

khadas@Khadas:~$ sudo apt update
Ign:1 https://dl.khadas.com/repos/vim3 focal InRelease
Hit:2 http://ports.ubuntu.com focal InRelease
Hit:3 http://ports.ubuntu.com focal-security InRelease
Hit:4 http://ports.ubuntu.com focal-updates InRelease
Hit:5 http://ports.ubuntu.com focal-backports InRelease
Err:6 https://dl.khadas.com/repos/vim3 focal Release
  Certificate verification failed: The certificate is NOT trusted. The certificate chain uses expired certificate.  Could not handshake: Error in the certificate verification. [IP: 135.181.182.36 443]
Reading package lists... Done
E: The repository 'https://dl.khadas.com/repos/vim3 focal Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Follow these instructions to fix it:

sudo sed -i 's/https/http/g' /etc/apt/sources.list.d/fenix.list
sudo apt update
sudo apt full-upgrade
sudo do-fenix-full-upgrade
sync
sudo reboot