I made the jump about a year ago at this point and have been happy with the choice. That said, there is a learning curve and everything isn’t sunshine and roses. I’d still rate it as fully worth it.

I think I need to pick a “distro”, right? Based on the above, which distro may work best for me?

Yes, though this is less of a “gotcha” than it might seem. Different distros will have advantages and disadvantages for different things. However, most distros are going to do most things at a reasonable level. It sounds like you are prioritizing ease of use and gaming; so, you may want to go for one of the more gaming focused distros such as PopOS or SteamOS. But, I would echo what @redlemace said, “take a live-distro, put it on an USB stick and boot from that. Yes, it’s sometimes slow/sluggish but it works and you can get an impression of the distro”. I ran my chosen distro from a USB stick for a bit over a month before committing.

what am I most likely to NOT be able to do, if anything?

Very little. However, you will need to relearn how to do some things. And you’ll probably have to get comfortable with using the terminal for some stuff. This can be a bit jarring for someone who grew up with Windows, as there are some things which just don’t have a GUI to configure. And some applications will need to be replaced. For example, you’re probably not going to be able to use Microsoft Office, but Libre Office is a good replacement. Photoshop will get replaces with Gimp, and so on.

Lastly, there are some games which just don’t work on Linux. A lot of that is around Anti-cheat software. For example, I wasn’t able to join my work team in playing Call of Duty 6. The EA Anti-Cheat is a complete “fuck you” to Linux users. So, check out ProtonDB for games you care about. Most games run just fine; but, there is the odd hole. Anymore, I’m more surprised that a game doesn’t work on Linux than when it does.

I have heard modding in particular can be challenging with Linux.

I’ve not run into this; however, I don’t use any of the mod managers (e.g. Vortex) and so I’m used to moving files around manually. I’ve also not run Skyrim on my Linux setup, and that does seem to require a bit of work to get going. So, this may be an issue, depending on the game. This is yet another reason to give the whole “install on a USB stick” recommendation a go. Spin up Linux, give modding Skyrim a shot. If it’s too heavy a lift, then maybe don’t do it. As much as I think Linux has been a good idea, it may not be right for everyone.

Are there some smaller indy games that don’t have Linux support (thinking back to the early mac days)?

Funny enough, I find the smaller indie stuff usually has better Linux support, but YMMV. For example, my son introduced me to Dome Keeper. It’s a small game, but it just worked and is one of my favorite casual games. Though again, checking ProtonDB is a good thing to do.

I would rate my computer technical ability at like… A 4/10. I haven’t done anything too crazy but can Google most issues and willing to learn. Is this realistically enough to get me up and running with Linux?

I’d think so. There’s lots of good info out there now to help you get up and running. Though this links back to the question about distros. If you don’t want to have to get super technical, pick a distro which is more aimed towards “just working”. And again, the USB “try before you buy” idea is really, really useful.

if the final answer here involves running a windows partition, is it possible to safely still use a windows 10 partition, even after the end of support?

Depending on how you plan to use it, the risk may be reasonable enough. For example, let’s say you have one or two games which just don’t run on Linux and you keep a Windows 10 partition around to run those games. You boot to Windows, play those games and then jump back to Linux for your normal computer use (web browsing, email, etc.). Then ya, that’s probably fine. The real risks start to show up when you use Windows for stuff which exposes it to the internet. If you are downloading and running random applications on it, you’re gonna have a bad time. Over time, even basic web browsing may start to be a risk, as vulnerabilities could be found which allow a malicious web page to run code. You also want to be sure you don’t have the device completely exposed to the internet (this is bad, even with an up to date Windows). Though, most home routers already prevent this; so, this is unlikely to be an issue. Just don’t hook your Windows 10 partition up to public WiFi (e.g. coffee shop, library or conference).

Just having the partition isn’t a risk. So long as Windows isn’t running, it isn’t available for attackers to attack. It’s just data on a disk. It’s only when it’s running and exposed to attackers that it becomes a problem. And you can control that and manage the risk.

anything else I might run into that I’m not expecting? Words of encouragement?

Be patient with it and it can be a worthwhile change. Also, don’t be afraid to come back and ask questions. There’s lot of folks here who can help you along. Getting away from Windows feels good and it’s great to actually own your system, rather than renting it from Microsoft. Best of luck.