Linux

LTS kernels aren't more or less stable. Rather, they have been selected by the kernel maintainers to get security fixes backported to them for a certain time.

Ubuntu does the same thing for the kernels on their LTS versions (technically they usually are not LTS kernels since canonical supports them instead of kernel team)

Overall I'd suggest going with what the distro provides unless you have very new hardware, in which case a newer kernel may be required

At home it probably isn’t worth it. Servers where changes can break things or is qualified against a specific configuration, more worth it. Often whatever your distro is providing is fine, even things like Ubuntu and soon Mint will be using non-LTS kernels by default.

How likely is my system to break with the standard kernel?

Unlikely. Standard releases are still pretty stable.

LTS just means Long Term Support in case you weren't aware. It means no new development is happening, but security exploits will be patched as soon as they arise.

If you just want stability, LTS is the way to go. If you want all the cutting edge bells and whistles and are okay with potentially some instability (but probably not much) then use the latest version.

If your device isn't connected to the internet during general use then I wouldn't worry too much about updating anything. Security fixes aren't important if there's no way to connect to your device.

Depends on the hardware you have. The fact you're asking this means these latest features wouldn't mean anything to you. I doubt you'd actually notice any difference.

My advice: use the LTS kernel if that's what your distro provides, only change if you find some hardware not working.

If you want stability use the latest Debian. The point of those LTS kernels is more and more supporting IoT and other devices you can't simply upgrade, but you want to keep secure... regular use cases can just usa a stable disto like Debian and you'll never notice any kernel related issues.

Stability isn't the same as unbreakability. It just means the update cycle is prolonged.

If you're worried about your system breaking, go for Fedora Atomic (Kinoite, Bazzite, uBlue, etc.).
It offers a very recent kernel (-> better hardware support, better performance, etc.) and because it's an image based distro, you can always roll back, so you'll always have a working and pretty much unbreakable system.

Do you need those features? If not, go LTS. LTS means you'll have to update the distro less frequently than latest.

If you want those features, go non-LTS, there's no other choice. If you don't want them, go LTS, it's less of a hassle.

It depends on your priorities, hardware, use cases etc. Honestly it's unlikely to be the determining factor. Available hardware and software support and your attitude to risk are probably more important. Fedora is a cutting edge distro with good reliability and is feature rich. It's upstream of Red Hat Enterprise Linux so has massive support behind it and a large user base. There are multiple spins if you want GNOME or KDE or an immutable OS etc. Adding additional repos such as RPMfusion make adding Nvidia and other proprietary drivers a breeze. As with most things GNU/Linux you need to be prepared to put in the effort to take control of your digital life. It's not easy but well worth it.

I’m running an LTS kernel on my desktop and a non-LTS on my laptop (both machine are running EndeavourOS). Both have been rock solid.

The only instability I’ve had is when I tried running a customised kernel (linux-cachyos)

I used to always go with Ubuntu LTS for dat stability. One day I had to upgrade to non-LTS version for some reason (that I completely forget) and I've never looked back. IME it's the same as LTS but with all the cool features you wish you had. Which I can't list rn because I forget.

...Who am I even. idk.

Don't worry too much about it if it doesn't make sense to you. It can be really valuable if you're deploying a substantial amount of IoT devices on the edge with no to little possibility to do over the air upgrades reliably or when the cost of failure is high (i.e. a technician has to be on site to fix it). So, sometimes you just want it to be running as stable as possible for as long as possible without management.

I have an LTS kernel as a backup in case something doesn't work with my main kernel.

Just recently I had an issue where my main kernel had a bug where snap's can't start up, so I just restarted into the LTS kernel to use it then restarted back into my main kernel.

It depends on whether you like your OS to be boring or not. If you like it boring and the LTS kernel works for you, use it.

Unless you're running a server, no.

You can install multiple kernels along with their respective headers. As long as you create a hook that runs mkinitcpio and grub-mkconfig whenever you update the kernels, you can then choose which kernel you want to use when the grub menu comes up.

This way you can always use whichever kernel you want, and is good practice should an update to one of the kernels have breaking changes.