To be an absolute pedant I think someone once made a proof of concept old school macromedia interpreter of some form, but its use was even more limited than the Java stuff which was barely of use itself. Similarly you could probably render it on a PC and have it transmitted to the DS like the various browser programs did. While the nature of the constant closed source updates and most people doing anything like open source versions of flash were caring more for the media playback aspects or utterly minor web stuff did not help matters I would also have to wonder if the DS could even handle it.
I should also say plenty of homebrew games were ports/recreations/homages to various flash games, which themselves were often all that to older games still (which in turn may have got said treatment or be able to be emulated). There were some interesting steps within those flash games -- I can't imagine anybody making a convincing case that Rampart was not the predecessor to tower defence type games but tower defence titles also changed things somewhat radically from that.