What I find attractive about keychords compared to modifier use is that keychords require less finger stretching
Fully programmable keyboards can do that, though likely not trivially. Its certainly doable with the QMK firmware (there is a
steno layer, that implements steno chording in the firmware), but not pretty yet. I have plans to implement better chording in QMK, but first I need to train myself on Steno a bit more, so I will actually use it too.
To be honest, if all you want is some chords, and not a full Steno system, its not all that hard: start recording pressed keys when the first key is pressed, and record until all of them are released, then consult the lookup table. Done, pretty much. With QMK, this is easy, a few dozen lines of code maybe (I'd estimate around 50 lines + docs, 70 if you want to make it pretty).