https://solarsystem.nasa.gov/news/859/nasa-funded-research-creates-dna-like-molecule-to-aid-search-for-alien-life/

If viable alternatives to DNA are possible, then we should be able to identify organisms that evolved totally independently of life on earth. And if more than one alternate working DNA can be synthesized, it suggests advanced alien technologies could seed the galaxy with tailor made life-forms capable of interstellar travel using starlight and stellar winds as a propulsion system.

Consider <micron-sized carbon/silicate dust grains or buckyballs saturated with genetic material encoded with the body plans of organisms, their future evolutionary history, and detailed mission plans within them. For a truly old and powerful technology it is not unreasonable to visualize interstellar travel not affected by a finite speed of light. There's your basic Expanse protomolecule right there!

Once the genetic material finds a suitable environment, organisms would arise, evolve, and carry out their programming, or parasitize existing life forms the way viruses commandeer our own cells' reproductive machinery. Its directed panspermia initiated by an aggressive, colonizing civilization, think of it as microscopic von Neumann probes, self-replicating machines at the molecular level. No anti-matter drive, space warp/wormhole, star gate or other superluminary tech required. All you need is plenty of time.

It has been calculated that at lower-than-light-speed, an entire galaxy could be colonized in just a few hundred million years with a simple Brownian or drunkard-walk dispersion scheme.