Devbox is a instant, reproducible development environments using Nix without the complexity. It handles nix-based, reproducible, shell scripts, and json config, and it's best suited for developers wanting reproducible dev environments without docker. Launched in 2022, it's a relatively recent entrant that's been gaining traction.

The core product is entirely free. Since it's open-source, you can self-host for free with no user limits. It's aimed at individual users, so it's fast to set up but may lack team-management features if you scale.