Sorry if there are other threads asking this, but I am getting a new DSi XL (which probably has no DSiWare installed). Is there another method of installing HiyaCFW?

A DSi XL will likely have Flipnote Studio on it, but if it comes without it, then the only method is hardmod.

Here: https://gbatemp.net/threads/dsi-downgrading-the-complete-guide.393682/Oh yeah, that's right. I completely forgot about the XLs coming with Flipnote Studio. But, just in case, is there a tutorial on the hardmod?
Thanks again @Robz8