I’ve seen people suggest Ubuntu without mentioning Kubuntu, but it seems like most people (especially gamers?) prefer KDE Plasma. I’ve seen people complain about Ubuntu’s GUI and lack of customization, but then no one suggests them to try Kubuntu instead. It seems like people just don’t know that Kubuntu exists.
Also as an aside, people often criticize how slow updates are on Ubuntu/Kubuntu/etc, but if you enable the backports ppa then it’s actually pretty quick!
sudo add-apt-repository ppa:kubuntu-ppa/backports


This is /c/linux_gaming. Recommending a distribution with outdated Mesa drivers is not in their interest, whether they know what they’re missing out or not. That’s among several reasons why Ubuntu in general is not a good recommendation for gamers.
Fair point about /c/linux_gaming. OPs question wasn’t really about gaming though and it was specifically about ubuntu/kubuntu.
So if anything, the OP should not have been in /c/linux_gaming, but the answers are on topic.
But even in regards to gaming, Mesa drivers are stable enough nowadays that even a bit outdated ones don’t make a lot of tangible difference unless you are hunting for every last frame. In which case a beginner’s distro isn’t for you anyway.
The average casual gamer will have no issues with Ubuntu.
Average casual gamer will have even fewer than “no” issues with Bazzite. There is no reason why (K)Ubuntu is preferable these days.
Apart from if they are going to use their PC for anything else than gaming.
Why would Bazzite be worse for everything else than gaming? It’s literally just a Fedora variant with some quality of life stuff preinstalled. All the stuff that (K)Ubuntu requires jumping through hoops (most notably Flatpak) is preinstalled and the entire software repository is officially supported unlike Universe in Ubuntu (KDE software is in Universe, hence why the backports PPA is pretty much mandatory).
It’s immutable Fedora. Immutability is something that not even regular Fedora uses, because it causes weirdness and potential trouble if you don’t just use it as a wrapper for flatpak.
Yes, it helps users not to accidentally break stuff. That’s a benefit for regular users, not a downside.
Even regular Fedora is a better alternative to (K)Ubuntu because of all that unsupported software in Ubuntu’s Universe repository. All software in Fedora is supported, not just a cherrypicked subset.