After about 30 years of Linux, here's my take on your questionnaire. Not sure if it'll add on what many others have said.

The one thing you have to remember is that Linux is not a replacement for Windows. It's a completely different operating system that lets you do the same operations in a different way. It can however run some of the same software thanks to a number of very clever hacks. That being said...

Will my ability to play games be significantly affected compared to Windows?

Significantly, no. Some things won't run, especially games that require deep anti-cheat hooks in the system. An awful lot of stuff will run fine thanks to the incredible work done by Valve.

Can I mod games as freely and as easily as I do on Windows?

Short answer: no. It often relies on software tools that won't run as easily. Sometimes, yes.

If a program has no Linux version, is it unusable, or are there workarounds?

Sometimes there's a functional equivalent in the Linux world, or you can get the Windows version to run either in a virtual machine or in a pseudo-emulated environment (Wine or bottles).

Can Linux run programs that rely on frameworks like .NET or other Windows-specific libraries?

Yes. they can be written specifically for Linux. Or they can be written for Windows and will work in Linux, sometimes (it's hard to get the translation layer right).

How do OS updates work in Linux? Is there a “Linux Update” program like what Windows has?

Every distribution manages this. It works by itself and is typically much cleaner than in Windows.

How does digital security work on Linux? Is it more vulnerable due to being open source? Is there integrated antivirus software, or will I have to source that myself?

The structure of the software in Linux (and the fact that it mostly comes from one source (the distribution) makes for a smaller target than in Windows where it comes from all over the place. Antivirus aren't used.

Are GPU drivers reliable on Linux?

They're the same as in Windows (the codebase is the same, the OS "glue" is specific). Other than the occasional bad release, they're usually OK. Linux is currently transitioning to a new display system, from X11 to Wayland, and nVidia is a bit behind on Wayland adoption. However, all three GPU makers typically work fine whether you use X11 or Wayland.

Can Linux (in the case of a misconfiguration or serious failure) potentially damage hardware?

Even voluntarily, that wouldn't be easy to do.

And also, what distro might be best for me?

Honestly, it doesn't really matter. They all install the same thing in the end. Just pick something mainstream and well documented and not something obscure.

Note that for X or Y reason, a given distribution may disagree with your hardware. It's the problem when everything is very specifically designed for Microsoft's OS, around specs that aren't fully publicly disclosed. If that happens, just try another.