I have tried and not working for me. (white screen when direct boot or no gift icon in native shell boot)
may I ask melonDS core version you're using and type of DSiWare file types?
DSiWare never been released to *.nds, however there are decrypted nds files exist as well as encrypted eshop format which contains titlekey.bin.. etc.
I've tried both types and wasn't able to launch for both standalone melonds nor retroarch's melonDS core
Only way I was able to play those dsiware games == install it to nand using standalone melonDS's manage DSi title menu.
