Same as with any Rockboxed device: submit the log manually.

For on-device scrobbling, I did get qtscrob to build in scratchbox by removing all mention of libmtp from the Makefile, but I'm utterly clueless when it comes to getting it packaged.

After installing by hand, however, it did submit without too much trouble, although I think I did have to use the recalc date/time feature.

Of course the easy way out (if not the most convenient in the long run) is to just hook it up to your desktop or use one of the web-based tools.