>One thing that I wonder is whether we could ever identify an alien communication signal as an alien signal is likely to be much more advanced.
This has always been my thing.
Scientists: "Well we've been listening for radio signals but haven't heard anything yet!"
What if they discovered radio but decided it was way too easy for others to spy on it, and be detected off planet, so they just used wired connections for everything eventually moving to 99.9999999% efficient fiberoptics and then when they became a multi system empire, after discovering jump-space, they just switched to using fast messenger probes that could pop in and out of a system and carry large amounts of data to be tightly beamed to and from planets via laser.
Or what if they don't use radio because they began exploiting the Glarfnuralka stream for FTL communications via their subspace ansible implants 50 years after they discovered radio waves?
What if there's something,just right there that we've yet to discover that is far more efficient for communications from an energy standpoint? We discovered radio waves 150ish years ago, we detected the first gravity wave less than 5 years ago. What if it takes us another year, another 1,352 years, to discover Glarfnuralkians and develop a way to reliably transmit and receive data streams in that stream?
Or what if Glarfnuralkians are also considered to be primitive and inefficient due to the limited number of effective channels in the stream and the fact that random bits of the data area always lost no matter what and that the nearest intelligent hegemony is instead using Glurrybluron entanglement to transmit in real time between dedicated units that involve some cesium clocks, some variety of variable gravity lock, proper magnetic containment chambers for dual singularities (and we're talking relatively small singularities here, if your containment chambers are advanced enough you can get this thing down to a backpack sized device), an adequate power source (probably some sort of zero point module that draws from the quantum foam between universes), a way to inject electrons into the containment chambers and sufficient computational power from some universe-on-a-chip quantum ASIC.
What if they discovered radio but decided it was way too easy for others to spy on it, and be detected off planet, so they just used wired connections for everything eventually moving to 99.9999999% efficient fiberoptics and then when they became a multi system empire, after discovering jump-space, they just switched to using fast messenger probes that could pop in and out of a system and carry large amounts of data to be tightly beamed to and from planets via laser.
Or maybe they're just really into face to face communication because of some sort of cultural/religious custom.
There is also the possibility a sentient species could have sensory organs that involve part of the radio spectrum which would likely prevent them from adapting radio communications.
They could be a species that uses chemical communication, not unlike many insects. You could theoretically convey large amounts of data this way with a moderate amount of evolution.