I'm not sure, but @Jake Bunce seems to be a relatively decent person to see about getting an import. There is no default importer, but you may be able to proxy import into XenForo via a different system.
Thanks to both Jake and King for the quick response! I'm getting the feeling that I will need to import into something else before importing into my final software. Now to figure out what best meets my needs.
Let me know if you find any potential pathway for accomplishing this. I have a local hobby forum that is entrenched in DNN and seems to intend to stay that way. Would really like to get them over to a newer engine that doesn't require constant laborious (and free) coding by one guy, who if we lose, we're screwed. I've been told me him that transition out of DNN is next to impossible without losing a lot of information, plus there is no handy conversion tool (at least not to vB, and I'm assuming that means not via another engine as well)
I have a potential solution for this. My current host for my sites is a board member on a non-profit org that ran a DNN forum, and they had someone who came up with a way to use the RSS feed to migrate over to vBulletin. He said it was messy and they lost some attachments but it was possible, and worth the trade-off.
He said they enabled RSS, recreated the users on the new site, and used an importer w/custom code to re-create all the forum topics.
I'm going to get in contact with the guy and find out some more details. This is the first glimmer of light I've heard of w/r to DNN transition
I am proud to report that I found a company that was able to successfully perform a conversion from DNN to XF. The site is running DNN (7.0 I think) and has been through several upgrades along the way, so it was a bit of a mess. There were 2 PM databases, and we weren't currently able to reliably access the older one (which wasn't able to be converted on upgrade 2 years ago).
The source database contained over 170,000 posts and over 150,000 PMs. They were able to transition 99.8% of all forum content, attachments, users, PMs, and more. I don't know at this point why the remaining 300 posts disappeared, but I was able to at least locate them by pulling the tables from the DNN MSSQL database into Excel and using Excel+DigDB to match tables with the XF mySQL database tables.
There is still other content that was "outside" of their standard transition package, but being a bit of a geek I have been able to figure out a few of these, including bringing over the user group associations.
Shockingly, the price for all of this was less than $400 (plus a LOT of my time). We did it as a dry-run so that we could evaluate the conversion and fine-tune it as needed, and then run the live site conversion at a later date once we develop the function and styling.
The result is that the site will continue down the path of transition to XF. It might take a few months...but I'm here to state loud and clear that it is indeed possible!