Version 0.5.2 implements a new workflow to automatically track the latest release tag.
You can now track the latest stable release of nix-flatpak with:
nix-flatpak.url = "github:gmodena/nix-flatpak/?ref=latest";
Or alternatively:
nix-flatpak.url = "github:gmodena/nix-flatpak/latest";
No new features of bug fixes are shipping with this release.