Yeah not in a way detectable to radio telescopes though. If an atmosphere is stoichemetrically ‘far’ from equilibrium, this implies a biogeochemcical process that is pushing it out of equilibrium.
Oxygen very quickly gets reduced out of the atmosphere. Thats the whole point of it as a bioindicator molecule. There aren’t many other species of molecule that are such a clear indicator of the presence of redox reactions. Preter oxidative respiration, If nitrogen was the electron receptor, but its species like ammonia might be visible via radio telescope. Google great oxygen holocaust. We know photosynthesis was happening before then, but oxygen wasn’t the terminal electron receptor.
Oxygen would be a smoking gun, because you don’t keep oxygen in an atmosphere if something isn’t replenishing it.