Upgrade Ubuntu to 23.04 / Ubuntu Lunar Lobster (development branch)

Open the Terminal and type the following command:

sudo do-release-upgrade -d

When this is done, check the result with the following command:

lsb_release -a

You should see this:

Distributor ID: Ubuntu
Description: Ubuntu Lunar Lobster (development branch)
Release: 23.04
Codename: lunar

See Lunar Lobster Release Notes: https://discourse.ubuntu.com/t/lunar-lobster-release-notes/31910