I have noticed that 'apk add' does not force-reinstall a package. I tried removing a file installed by a package (on the target) and run sideload again, but the file I had deleted was not restored.
I assume apk skip re-installing packages already installed.
Assuming my understanding is correct, my rather trivial solution is to run 'apk del' + 'apk add' to force-reinstall a package.
This MR adds a --reinstall option to pmbootstrap sideload to do exactly that.
Happy to learn if there are more educated ways to obtain the same.