Thank you for your suggestion. After browsing the site you cite, I find two things:
-
There is another, potentially simpler, work-around: if I enter “sudo apt update && sudo apt upgrade” in a terminal window, the updating proceeds without a problem. There is no complaint of insufficient space. I have done this now several times without a hitch.
-
There are many reports of systems becoming unusable after a kernel update. This is potentially a serious problem. Because the procedures for kernel updates for Raspberry Pi are very different from what is done with other Ubuntu installations (and poorly documented), the usual things one does on an Intel-based Ubuntu are not available. There is no grub2 to allow you to choose which kernel to boot (after, say, a problembatic kernel update); and there is no knowledge base I can find that offers maintenence tricks, such as using Synaptic to remove linux-image and linux-header packages that constitute kernels that are no longer needed.