I have tested https://salsa.debian.org/debian/gpgme/-/merge_requests/1 and it works fine. I would however name the new package gpgme-json, not libgpgme-bin
The package is only providing gpgme-json(1). If it is going to ship more binaries in the future, it can always be replaced. If someone is told they need gpgme-json the expected package name is 'gpgme-json', not libgpgme-bin. Plus, that lib prefix is even more confusing. Even the description (“This package contains the gpgme-json binary to access GPGME...”) seem to ask for that name. That is the only nitpick I have. It "just works". :-) The debian/changelog would need updating, and rebased on top of gpgme 1.18 (bookworm/sid) from the current 1.14.