dosbox-staging: 0.78.1 is not a release yet
According to Repology, Alpine packages dosbox-staging version 0.78.1. Such release does not actually exist, see this discussion for explanation of the v0.78.1 tag in upstream GitHub.
I am not a regular Alpine contributor or user, (but maintaining the dosbox-staging package in Fedora,) but perhaps you want to revert to the latest released version v0.78.0 or mark the package as a release candidate or such?
Mentioning @psykose @mps as people listed as maintainers.