Well, bonbob, I owe you an apology.
I've just installed TCL 8.2 (x86) on an old Dell desktop and swapped my RT5370 over from the Raspberry Pi. And indeed I cannot get the dongle to work either, no sign of any firmware or driver activity in dmesg, whereas it works fine under piCore. Like you I can see the dongle in lsusb but it's inactive and has no drivers loaded. I have firmware-ralinkwifi and wifi extensions in onboot.lst and see them mounted.
It's not a solution to your problem, but at least I can confirm that one seems to exist.