what kind of tools do people use to make music that sounds somewhat Gameboy-like?  I want to try my hand at making music for my submission, but creating any reasonable chiptune music feels out of reach with my novice skills/tools (which basically amounts to opening GarageBand, praying, and sliding notes around until I get something passable).

If you're new to making music, you might want to check out some free chiptune VST plugins. The genre itself is called Chiptune—you can look it up on YouTube or elsewhere.

There are also emulators for old audio chips, like Furnace, though they can be quite complex to use.

Otherwise, just look for chiptune plugins and presets for them. I'm sure you'll be able to find a DAW to use.

If you're willing to dig into it, Famitracker is free and what I used for my work on this Jam :)

I use Famistudio, and its basically Famitracker but more DAW-based like FL Studio and Ableton. Once you figure it out its fairly easy