I think the drake equation is too Anthropocentric it assumes what I think are strange things. Life has to be based on liquid water, radio is somehow obvious and inevitable.
My bet is that there is a much better way to chat between stars than EM, which drops off as the inverse square of the distance, and travels at c. It's terribly inefficient. We might outgrow radio in 50 years, and thereafter consider our SETI radio efforts as quaint.
I was just watching the great Neil deGrasse Tyson talking about that. The most common elements in the universe are, from most common going down: hydrogen, helium, oxygen and carbon. So if water is just two atoms of hydrogen and one of oxygen, it might not be all that unlikely and maybe even the rule. Anyway, it looks like the best bet. https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...
I think even the great Tyson may be thinking like a human on this one. To think that life has to be chemical is also Anthropocentric. The requirements are complex systems that can ratchet and allow emergence. The number of those is measurable.
I was not thinking quite as exotic but I like where you are coming from. Physics:
Mechanical processes weather, erosion have emergent properties.
gravity is not impossible N object systems where N>2 tend to be chaotic and thus have a possibility of emergence and ratcheting. The universe is chock full of chaotic and emergent systems really it is harder to find one that is not. If a system has the properties of variation and selection than it can produce life.