Alfred Apple

From start to finish, here's how I did it.
 
Go to the following link, download build root, unzip it and 'cd' into the directory:
https://git.busybox.net/buildroot/
 
Then issue the following commands that are in italics and follow the bullet point directions.
 
make friendlyarm_nanopi_neo_defconfig
          - Where friendlyarm_nanopi_neo_defconfig is the name of your board's def config located in the /buildroot/config/ folder
make menuconfig
         - A UI will pop up and you can add/remove packages or libraries from here. ie: Python, nano, libgpiod, etc... (Use "/" key to search)
make uboot-menuconfig
         - This is the direct answer to OP's question
         - From this prompt, scroll all the way to the bottom
         - Device drivers --> USB Support --> Uncheck all boxes
         - There's also another option to reduce boot time. Go all the way back to the first page of uboot-menuconfig
         - Change delay in seconds before automatically booting to 0
make
 
This will output /output/images/sdcard.img. use Etcher or w/e to write to sd card like usual. Make command took ~1hr to compile the first time so...
The link below is a NanoPi Neo image, with no password. It boots in 4 seconds and has Python, libgpiod and nano installed and nothing else. No USB or Ethernet.
https://fastupload.io/2vykAzhretXuft1/file