I see that I've returned just in the nick of time.
Yes, you can can bread. There's defense-funded research from the 40s about how to do this safely. Basically, you have to keep the moisture below a certain level and maintain a certain acidity. My understanding is that it is difficult to achieve these goals and have a tasty treat. Although I did recently have an MRE with "pound cake" that was delicious. Obviously, it wasn't an equal-ratio cake, but it was the best thing I've found in an MRE.
It's become popular to can nut breads. Nut breads are, if done correctly, moist, so it's not compatible with the research findings. I found a formal study of the practice in a peer-reviewed scientific journal a while back. They intentionally introduced C. botulinum before canning and measured the amount of toxin after so-many days. The conclusion, not surprisingly, was that canning the bread did not kill the pathogen.
I feel like I've written this out here before but I can't find it....
There's a German tradition of steaming bread. Black bread and the like. I assume this was due to the curse of rye, which grew readily, even in bad years. If it was a good year for wheat, there was a respite, but otherwise you had to deal with rye-based bread. The rye flour holds moisture more and is difficult to bake. By steaming the bread, it didn't burn even when baked for a long long time. At least, that's what I've pieced together over the years.