After noticing lxc/lxc-ci/issues/960, it turns out a recent commit 194b0f4 introduced support for release candidate versions. From what I can see, while the release picking logic (last item lexicographically) worked well for stable releases only, it doesn't anymore when rc releases (e.g. 25.12.0-rc5) are involved, as they always appear last after the corresponding stable (e.g. 25.12.0), which never gets selected.
After noticing lxc/lxc-ci/issues/960, it turns out a recent commit 194b0f4 introduced support for release candidate versions. From what I can see, while the release picking logic (last item lexicographically) worked well for stable releases only, it doesn't anymore when rc releases (e.g. 25.12.0-rc5) are involved, as they always appear last after the corresponding stable (e.g. 25.12.0), which never gets selected.