Linux

As a KDE fan, I had some bugs on some devices (like on one of the laptops, wallpapers did not install correctly and the setting to always show battery charge didn't work) even on Debian 12.

XFCE is well-known for stability, but seems to be increasingly irrelevant for the average/newbie user because the interface looks outdated and configuring is relatively complicated.

Interesting you mentioned Firefox ESR - iirc, even at release the version shipped with Debian 12 was considered very old, prompting many to install Firefox as a flatpak. Two years later, it's two years older.

Flatpaks are good and suitable options for many tasks - no argument here! But some things are just better installed natively, and there Debian just...shows.

Steam is a godsend, but there are many non-Steam games and, importantly, programs out there, and launching them through Steam often feels like yet another bloated and slow workaround; besides, you cannot choose Wine over Proton, and sometimes (granted: rarely) you may want to use Wine specifically.

To conclude - it's alright to choose Debian anyway, it is good! But I just feel like newbies and casual users could save a lot of trouble and frustration simply going with something that doesn't require all that - say, Fedora (non-atomic), or OpenSUSE, and then go from there to whatever they like. There are plenty of distributions that are stable, reliable, but without the tradeoffs Debian sets.

If you feel like stability is your absolutely biggest priority ever, and you have experience managing Linux systems - by all means, go Debian. But by that point you'll already know what you want.