You need a runner for scripts that follow the PEP (actually the packaging standard established initially by the PEP, hence the note about it's historical status.)

The two main runners I am aware of are uv and pipx. (Any compliant runner can be referenced in the shebang to make a script standalone where shebangs are supported.)

The shebang line references uv.

Is it time for a Debian `alternatives`-style system for PIP 723 compliant Python wrappers yet?

I could totally see `#!/usr/bin/python723` become a thing :)