plus there’s drivers to consider

Is there an issue w/ drivers on unlicensed Windows? And yeah, you can reuse the key your computer has, this is assuming you can't for whatever reason (i.e. laptop shipped w/o it).

I’ve never found the place to do it easily in the GUI in Mint

That would depend on which flavor of Mint you're using. Keybindings are almost always in the GUI, though you can also do it through the CLI in many cases (e.g. GNOME-based DEs use gconf/dconf IIRC).

I haven't used any of the Mint flavors, so I won't be of much help. But surely someone in one of the Linux communities could help (or just search for "change keybindings Linux Mint" or something).

OpenTTD

Oh yeah, OpenTTD rocks. I haven't played any of the others (other than messing w/ Minetest when it first launched), so I'll have to check them out. :)

Most of my gaming is on Steam, and many (most? haven't checked) of those don't have DRM, since I mostly play indies and older games because I think newer games tend to suck.

We need to pay for the more expensive software because of our tax situation

That's too bad. It's still worth a look IMO, online tax software has come a long way. Unless, however, you're doing something fancy with businesses and whatnot, but at that point I'd just hire an accountant. Anyway, at 80, it's probably not worth making huge changes, though I'd strongly recommend putting some checks in place so granny doesn't easily get scammed (and I'm guessing you already do).

Anyway, I'm always happy to see someone trying out and enjoying Linux. I've been here for >15 years, so I've kind of lost touch with what people on Windows use these days. I do remember the transition being a little rocky, but after a year or so, I ditched all of the Windows crap and found solution to everything I need.