I currently run windows 10 on my main desktop PC, and also have a steam deck that I sometimes use in desktop mode instead of my desktop. With the way Windows is going, and the way Linux Gaming is dramatically improving, I might consider ditching Windows, at least for the most part, on my next PC build. What would be the best distro to use for gaming, with casual use as well? Any suggestions?
Whichever one you enjoy using.
Unless you have some special hardware need, all the desktop distros perform about the same. (Even long-term support releases, which offer newer kernels in case you need them.)
One can use backported version of software in Debian, I use it and it works good so far.
If you're using a LTS release then you should be aware that many of the programs in the repository will only get bug-fixes and security updates until the next LTS is out. You can get around this by using the Flatpak versions of those programs instead of the distribution's versions.
Nonsense. Long-term support (LTS) generally lasts until either a predetermined date or until multiple subsequent releases are out. I don't know of any that stop when the next LTS release arrives, but if such a distro exists, it is atypical.
Recent examples:
https://ubuntu.com/security/CVE-2023-38546
https://tracker.debian.org/news/1470204/accepted-curl-7740-13deb11u10-source-into-oldstable-security/