Assembly theory approaches the question from a different angle but largely reinforces this conclusion. Essentially, anything past a significant level of chemical complexity is a sign of life. DNA is astronomically unlikely to form spontaneously. It was designed by co-evolution. If you find a screwdriver on an alien planet, you can deduce the existence of screws, machines that require fasteners, and ultimately a living being that built those machines.

In the history of the universe, we only know of a single instance where something ejected from planetary atmosphere by its own force. Humans, when we launched a rocket into space. That's it. Debris enters planets atmosphere but we never see a rock LEAVING an alien planet on its own power. Except on earth.

A planetary system with evidence of panspermia would be a similar phenomenon to DNA, a screwdriver, or a rocket - clear evidence that life was at work to produce something otherwise so implausible.

This works so well as a framework for finding alien life since it makes no assumptions about what life is or what it consists of. Only that it produces complexity.

This sci.news summary is kind of dumb:

Outside of creating an artificial origin of life on Earth, the primary targets for the search for life are planets inside or outside our Solar System.

You don't say! Both inside and outside our Solar System? Steady on, chaps!