So after pulling out some hair over the last few days, I figured I would post an update. Interesting things happen when you go over spec with the 5070.
My unit came with 4GB in a single DIMM. The eMMC drive had been wiped. I installed Windows 11, which filled the "drive" completely. Installation went as expected and took 10-15 minutes, as I recall.
I received a few days later a pair of 16GB DIMMs (32GB total) and a WD Blue SATA SSD. I installed both with the plan to wipe the eMMC and reinstall Windows on the SSD.
I booted, pressed F1 to continue after the memory size change notice on screen and continued to boot Windows 11 Setup. The boot took about a half hour and everything from the point on took orders of magnitude longer to accomplish than it should have.
Windows 11 took about three hours to install, errored out on "OOBEREGION" which I was able to get through. It errored again on "OOBELOCAL" and I couldn't continue past that point.
I tried Windows 10, which got about as far in at least that amount of time, and errored out on "Your system restarted... we may be able to download an update which fixes the problem" or some such. That was a dead end as well.
Thinking that the SSD might be bad and realizing that the likelihood of that was remote, I removed the two 16GB DIMMs and reinstalled the 4GB DIMM.
The machine was immediately fast and I was able to wipe the bad Windows install from the SSD.
Next I tried only one of the 16GB DIMMs in place of the 4GB DIMM. The machine was fine and I reinstalled Windows 11 to a wiped SSD.
My BIOS is 1.15.1, the latest, I believe.
I also believe there's a problem in the BIOS where the machine does recognize 32GB installed but doesn't act properly.
So now, I am running with a single 16GB DIMM installed. I wish it were a pair of 8GB DIMMs, giving me dual-channel, but it is what it is.
The 5070 is a nice device. Mine has a Radeon GPU installed and supports up to six displays. But the device is not without its quirks.