But none of it is intelligent. Anaerobic processes are drastically slower and less efficient than aerobic ones. I wonder if a functioning brain could even work anaerobically. 20% of our oxygen consumption is done by our brain.
If we find any life at all on Europa, intelligent or otherwise, it proves that earth is not the only planet with life. It’s an obvious conclusion but if we find alien life even in our own solar system that says something about the prevalence of alien life.
There are some multicellular anaerobic organisms, such as a few species of Lorificfera. It is worth noting that they all appear to be descended from aerobic ancestors that lost their ability to process oxygen. Multicellularity is very difficult to evolve, and has only happened a few times.