Wow millions or none.

"We have absolutely no idea" explained scientists.

When the Americas were discovered people speculated about all sorts of things like fountains of youth, enormous stockpiles of gold etc. I think the same speculation nonsense is fueling these sorts of projections.
Can't say I know what the others don't, but the fact that we have yet to discover any radio broadcast should prune these optimistic assumptions. Even if we were to say only intelligent life is rare, one has to wonder what the probability of using radio waves would be just as a biologic process by relatively unintelligent creatures. Animals in the deep ocean use light to communicate, doesn't seem that implausible that a creature on another world could use radio to communicate with members of its own species. Such radio broadcasts would not have the speculated to be short period of intelligent life. They should be uninterrupted for millions and millions of years. My guess is that 1 in 5 worlds with nervous system level life probably would have animals with radio communication capability. The fact that we have not picked up a one, is not encouraging.
It still could be that life is all over, but just not at the animal level (something with a nervous system and ability to move and make choices in actions). More like single cellular stuff or plants and fungus level stuff.
It is also possible that our radio antennas are just too insensitive to detect radio waves from biological sources across space.

I know I am not the first to say this but if there are many planets with intelligent life, many would be older than ours and probably advanced much farther than we are. It is much more likely they will come here than any chance that we will go there.
These models also seem to always leave out most of the unique things about our planet that make life possible. If our planet didn't have trees for building and fuel along with easily obtainable minerals, we would still be in the stone age. If our percentage of oxygen was a little higher or lower we wouldn't have fire or it would be uncontrollable. So many requirements must be met for higher life forms to advance. Even with millions of earth sized planets in the Goldilock's zone, the odds of intelligent life are slim to none. I suspect most of them are like Venus or Mars.

We had to speculate in my Advanced Astronomy class, UT Austin --circa 1980-- as to the very existence of planets as none had been discovered yet. One area that we discussed was that it might be very important for a potential LIFE harboring planet to have a Moon that created tides... Might was the operative word. If Mars has life or once had life, then, never mind.
Per Drake's Equation, I found the notion that civilizations have some kind of end of civilization life, most troublesome, thus limiting the number of civilizations based on what is pulled out of thin air per a X variable. It could be that if a civilization exists long enough, it will be hard to snuff it out.
I did suggest that a civilization/people might de-evolve. See the movie, Idiocracy.
Per radio waves: We discussed this in depth. The "WOW" signal --1977-- had been detected by then, but never found again. We speculated that distant signals, unless willfully directed, would be hard to detect anyway. Recently, as in this year, quantum jump transmissions have been played with. Arecibo would be useless here. There was discussion on how much more advanced means to detect and to put together distant radio signals, might be achieved. We are just really beginning so it seems to me.
It could be that we have bits of signals smattering all around us and we just don't know it --yet--. All exciting!

Another Scientific Wild A$$ Guess. Let's find ONE before we start predicting 100 million!

100 million planets in the Milky Way 'may' support complex life--'may'. Pure conjecture really.
But remember, the Milky Way is made up of some 300 BILLION stars. That's a pretty thin scattering of 'maybe' complex life. Here's hoping, but don't expect to be shaking appendages with aliens anytime soon.

I rather think that advanced intelligent species just don´t live on planets. Technology tends to have a very heavy footprint... one that damages the environment. That should be true for any technologically advanced civilization. You cannot get something for nothing... Advanced civilizations must therefore live in free space or at least in interplanetary space (in habitats a lá O´neill). Most of the time their comms would be strictly a line-of-sight system, like laser. They simply have no need for onmidirectional comms (like radio) and the associated high energy demands. B.T.W, directional comms are a must in a heavily colonized cislunar or interplanetary space!

If there is no other sentient life in the great beyond, then describing me as the only blue-eyed person on planet earth would not come even close to the rarity of the human species in the universe.

yrag: Here's some "impure conjecture". We know all complex life was killed off here 4 times. We don't know if some had become sentient. For example, if life here went back to "reset" again, which will happen for sure some day, and we have not stopped fighting long enough to establish a colony elsewhere, will evidence of our existence remain? Future sentient species may find no trace of us.
No search for ETs was possible until last century. Space travel, exploration, and ET contact is a very low priority compared to killing each other. While TPTB waste the masses wealth on building weapons of species extinction, the masses cheer them on. People who specialize in killing other people and breaking things get standing ovations. Scientists, not so much. There are no memorial graveyards for them. The same can be said for the everyday family businessperson and the industrial giants. History emphasizes war, not science or business. How many businesspersons have gotten the Metal of Honor? Even the ones who were considered the pillars of society were vilified later by pseudo sociologists as "robber barons".
And last but not least, in fact the most crucial people to survival, the philosophers who gave us the sciences, mathematics, ethics, and economics, are unsung in school compared to people who contribute little or nothing.