Here is what I get with dpkg --info alire_1.2.1-2_amd64.deb after building it:
new Debian package, version 2.0. size 3434464 bytes: control archive=1560 bytes. 476 bytes, 13 lines control 2386 bytes, 35 lines md5sums Package: alire Version: 1.2.1-2 Architecture: amd64 Maintainer: Stephane Carrez <stephane.car...@gmail.com> Installed-Size: 17740 Depends: libc6 (>= 2.35) Section: devel Priority: optional Homepage: https://github.com/alire-project Description: Ada package manager. A catalog of ready-to-use Ada libraries plus a command-line tool (`alr`) to obtain, build, and incorporate them into your own projects. It aims to fulfill a similar role to Rust's `cargo` or OCaml's `opam`. As you can see, it does not depend on libgnat-12 and does not even recommend gnat. This seems suspicious to me. Could you please check that the dependencies are generated correctly? -- Ludovic Brenta.