@dureal99d I’m not sure how dd-wrt handles vendor classes, but I’m pretty certain it can.
What’s likely happening with your problem is dd-wrt is only setup to serve a bios boot file, which is why most of your uefi ISOs don’t work.
Perhaps one of the @Developers or @Moderators or @Testers have dd-wrt at home and know how, but you need to set it up to hand out ipxe.efi for uefi identifying machines and undionly.kkpxe for BIOS identifying machines (generally).
If you read through the article I posted you might better understand what you need to do with your dd-wrt router.
Here’s something I found by searching Google for ‘dd-wrt dhcp vendor class’. The thread is probably so old that it doesn’t even apply to the latest version but it might point you in the right direction:
http://www.dd-wrt.com/phpBB2/viewtopic.php?p=643566
Another idea is to turn off dhcp on the router temporarily and then edit the fog servers /opt/fog/.fogsettings file and change do dhcp and bldhcp to yes or 1, and rerun the installer and just see if your ISOs work then. Because FOGs dhcp setup already well supports many architecture types, some of that work I contributed to, it’s solid. To undo this, same steps but turn those two settings off, then manually stop and disable dhcp. For Ubuntu it should be service dhcpd stop;service dhcpd disable
Here is more info on .fogsettings if you get lost or curious:
https://wiki.fogproject.org/wiki/index.php?title=.fogsettings