Hi! The F-Droid reproducible builds & verification effort recently led [1] to the development of apksigcopier [2], a tool to copy APK signatures from a signed APK to an unsigned one.
( I've started packaging it for Debian [3] and intend to file an ITP soon, but since I'm not a Debian developer -- yet, though I'd like to become one -- I could use some help with that. ) - Felix [1] https://gitlab.com/fdroid/fdroidserver/-/merge_requests/802 [2] https://github.com/obfusk/apksigcopier [3] https://salsa.debian.org/obfusk/apksigcopier/-/commits/debian/sid