You can safely assume that one of the fundamental forces of our Universe is the same, namely electromagnetism, which means that yeah! AM/FM radio would be among those signatures.
So the next hundred years of human advance, I expect, will bring similarly transformative changes in the ways we communicate and the shape of our "technosignature".
Our expectations for what other species might be doing don't seem to be informed by the things we know we've done.
We are basing what we consider natural phenomena on our observations of the galaxy.
If we were to flip the assumption from life being rare to life being pervasive, what assumed natural phenomena could in fact be evidence of life?
There is precedent for this on Earth. We are just startign to discover how much The Amazon rainforest is actually a human creation and basically a massive multi-generational bioengineering project.
This is not a serious position fo mine, btw, I know that we can track most astronomical phenomena back to fundamental laws of nature.
But equally there are some massive astronomical myseteries (dark matter/energy, certain stars being more/less common than expected etc) and I can't quite dismiss the wonder that our baseline assumptions have been tainted by this assumption.
There's your Fermi paradox, we live in a dumpster pile.
Lines up great with my self-esteem.
It looks like using only old technology we can detect the signal and identify it as a artificial signal, but it would be very hard / impossible to decode.
Granted, you'll not be able to differentiate between them, only that they exists. And at this point of searching for those signatures that's all you need though. Also Marconi was listening to lightning strikes generating radio waves using his radio, and that was over a century ago. Lightning strike generates radio waves all over the spectrum, so we had this capability right from beginning.