Update:
- I was able to flash the SD with Raspberry Pi imager
- I had to download a pre-built balena image and copy the config.txt and cmdline.txt contents over to the respective files in my built image; any way to get those options to generate by default in the yocto build process?
- The USB bug is indeed fixed. This was the original reason why I built the image. Woo!
Thank you all so much for the help!