Starting with Ubuntu 22.04 (Jammy), PhotoQt is available in the official repositories (universe). Of course, this PPA will be continued to be provided for older versions of Ubuntu, and in order to always stay on the latest version of PhotoQt. However, if you want to try PhotoQt out, installing it from the universe repository is a quick and easy way to go about that.
Open a terminal and type the following one line at a time (don't include the dollar symbol):
$ sudo apt-add-repository ppa:lumas/photoqt
$ sudo apt update
$ sudo apt install photoqt