So I checked a few things.
My SD card was a Kingston 16 GB Class 10, rated for 45MB/sec. It should be
The power adapter was a Samsung unit rated at 2A at 5V. I replaced it
with a unit rated at 2.4A at 5.25V.
I rewrote the SD card. I used gparted to resize the root partition to be
the remainder of the space on the card. It was 3.2GB with 2.3 GB used.
Now it is ~12GB with 2.3 GB used. I wanted to resize the swap partition,
which is set to 488 MB. For some reason gparted wouldn't let me touch it.
I rebooted and reinitialized things. It runs much, much faster, but it
still seems slow. Each package upgrade in #dnf upgrade is probably taking
a minute now, versus 5 minutes before.