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Adventures & experiences in contemporary technology
The Flatpak concept offers a useful way of getting the latest version of software like LibreOffice or GIMP on Linux machines because repositories are managed conservatively when it comes to the versions of included software. Ubuntu has Snaps, which are similar in concept. Both options bundle dependencies with the packaged software so that its operation can use later versions of system libraries that what may be available with a particular distribution.
However, even Flatpak depends on what is available through the repositories for a distribution as I found when a software update needed a version of the tool. The solution was to add PPA using the following command and agreeing to the prompts that arise (answering Y, in other words):
sudo add-apt-repository ppa:alexlarsson/flatpak
With the new PPA instated, the usual apt commands were used to update the Flatpak package and continue with the required updates. Since then, all has gone smoothly as expected.