On most Linuxes one would typically use
usermod, but Alpine doesn't seem to have it, is there some other way to set home directory on Alpine?
usermod on Alpine, you could try installing the
shadow package of the community repository:
apk add --update shadow
Tip: when looking for a particular Linux executable which isn't readily available on Alpine, Alpine's package search engine is very useful:
As Alpine's popularity is steadily increasing, more and more packages are added, so there's always a good chance to find the package you're after.