"Selection mode" is supposed to be a new feature in KDE Gear 22.12 and I want that in 22.10.
Another new feature is Selection Mode. Hit the spacebar (or tap the hamburger menu and check the Select files and folders checkbox) and a light green bar will appear at the top of the file view (see video). You can now click or tap files and folders and quickly and easily select the ones you want to work with.
But Kubuntu 22.10 only has KDE Gear 22.08.
Updating with backports PPA there is no change.
Upgrading to daily versions of the OS will most probably leave you with a very buggy system. I keep this answer for reference, but I advise against putting it into practice. (That small new feature is not worth all the effort, not even the one to upgrade, and especially not that for downgrading and fixing the resulting problems.
At least for the moment, Gear 22.12 is not available in Kubuntu 22.10 backports, but is in testing/unreleased/daily 23.04 Lunar Lobster. In order to upgrade from 22.04 to 23.04, taking the risks that come with using unreleased versions, following this tip, I have downgraded from backports back to 22.10:
sudo ppa-purge ppa:kubuntu-ppa/backports
restarted, updated:
sudo apt update
sudo apt upgrade
then:
sudo do-release-upgrade -d
(This proved helpful.)
In the end, the daily build proved too buggy (network not working after suspend, various crashes, shortcuts and tray apps not working until restart) and I have succeeded in downgrading back to 22.10 by using this method. More here.