Raspberry Pi troubles solved

After updating the software (using apt-get) on the Raspberry Pi I use to run OctoPrint to control my 3D printer, it would not recognize my TPLink USB WiFi dongle.

Turned out that the firmware needed for it has been removed from the Raspberry Pi kernel, so the fix as presented here was to do:

sudo wget https://github.com/lwfinger/rtl8188eu/raw/c83976d1dfb4793893158461430261562b3a5bf0/rtl8188eufw.bin  -O /lib/firmware/rtlwifi/rtl8188eufw.bin

I had some other problems too, apparently I must have powered down the RPi messily. I had to use the Mac's Disk Utilities to repair the boot partition (Windows FAT format), then load a Linux virtual machine and copy the start.elf file from another copy of the distribution to my boot partition.