I formatted an SD card for use in a Raspberry Pi, in fat32 format using the GParted and following the steps in this post.
But then Ubuntu didn’t recognize it, so I couldn’t put the NOOBS files on it. I went around in circles before giving the SD card a label, a step described as “if you wish” in that post. Voila! My SD card was immediately recognized.
That’s all. Label the volume. Maybe this brief post helps someone searching the internet, but if nothing else I hope writing this makes me less likely to fall in this same trap again.