Linux

The are plenty answers already, but also I will respond in order to give you more opinions, so, you can have a more open view about what users do think about linux.

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

Yes. In windows you put the .exe in some folder and then double click to play it, easy. Nowadays games come with a client, like Rockstar Social Club, or the Ubisoft launcher that handles your account and manages game updates. In linux, even if you had only the .exe you still had to make an uncertain number of tweaks to achieve running the game, but, with the clients, you need to do both, find the correct tweaks to run the client and do the correct tweaks to run the game next. Even with modern solutions, like Proton, we strugle with games running in Linux. See there are no silver bullets.

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

If you find trouble modding games on Windows, you also will have a bad time in linux.

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

You can use WINE to give it a shot. There is a probability that works very well. But, like games, you will need to make tweaks to work properly. I had this problem with Rufus, there is not linux version, so you can run it with WINE, the problem is that Rufus under WINE doesn't reconogize your usb pendrives. Till this day I do not know how to fix that.

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

Thankfully we have dotnet core now, the thing is that the library or software must have been compiled with it to work in linux. There is also Mono.

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

If you use a distro, like Linux Mint, there will be a job that will check for updates and then warn you. Normally, updates are done manuallly (sudo apt-get update, for example). The other thing is doing your own update script job that runs automatically weekly or monthly.

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?

This is a computers knowledge concern, most linux distribution have this disabled by default. Your resposability as linux administrator is set up your own security metrics. I use fail2ban, ufw, clamav and openssh. Very basic, if you ask me.

Are GPU drivers reliable on Linux?

With AMD hell yes. But, since I have never used Nvidia before my answer here could not be the most valuable, empirically speaking.

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

The most probably thing that can happen to you is break your boot system. Hardware will be fine and you can always reinstall Linux/Windows with its default boot.

And also, what distro might be best for me?

As you want to play games, and, I do imagine that you also want linux as you main PC, I would recommend Linux Mint to start, all the documentation avaible for debian easily apply for Linux Mint, I mean, if you can't find some specific solution in the Linux Mint documentation.

My last two cents are the next ones: if you can, use windows just to play things and use linux for everything else. It works for me and may work with you. Cheers.