In the book Foundation and Earth I think it is stated that no other alien life had been found in the galaxy that didn't originate from earth.
However, in the story "Victory Unintentional", collected in The Rest of the Robots, there are some alien creatures on Jupiter called Jovians. Since Foundation and Earth connects the Foundation universe with the Robot series, is this story canonical in the Foundation series?
They are part of the same universe, but note that Foundation and Earth is set long after "Victory Unintentional".
The three robots — ZZ One, ZZ Two, and ZZ Three — were built by the United States Robots and Mechanical Men Corporation, the employer of Dr. Susan Calvin featuring in other stories. So this ties them to the Robot-series and through that, to the Foundation-series.
Foundation and Earth is set roughly 20,000 years after The Caves of Steel, which is set in the 50th century AD. We have no date nor chronology for "Victory Unintentional", but humans seem to have only recently developed force fields good enough to travel through space. Quite likely they haven't left the solar system yet, which puts the story quite some time before The Caves of Steel.
Also, Earth is quite hard to find in Foundation and Earth, as is the entire solar system. This leads us to the conclusion that either the Jovians have perished in the 20 millennia that have passed (perhaps their "eternal peace" wasn't as eternal as promised, and they lost), or that they never left Jupiter and were forgotten like Earth was.
Isaac Asimov himself disavows the notion of complete consistency.
The fourteen books [...] offer a kind of history of the future, which is, perhaps, not completely consistent, since I did not plan consistency to begin with.
Prelude to Foundation by Isaac Asimov, "Author's Note" (preface).
Asimov did not consider "Victory Unintentional" to be part of the Foundation universe. In his autobiography In Memory Yet Green, he wrote that the only story with extraterrestrials in the Foundation universe is “Blind Alley”:
I suggested to Campbell that I do a short story I planned to call “Blind Alley” [...] Campbell laughed and agreed, and on September 2, I began it.
It was the one story written in the Foundation universe (whether part of the Foundation series or not) in which there were extraterrestrial intelligences. In all the other stories, a purely human Galaxy is described, with no other intelligent beings present and with no unusual or monstrous animals either.
In Memory Yet Green, 1979
Furthermore, he regretted placing “Blind Alley” in the Foundation universe:
“Blind Alley” was not really written as a Foundation story. I used the Galactic Empire background because that was convenient, but I was eventually sorry that I did, because there is just no room for any non-human intelligent species in the Foundation universe.
From a letter to Joseph F. Patrouch, quoted in The Science Fiction of Isaac Asimov, 1979
In Foundation's Fears by Gregory Benford it is suggested that a wave of explorer robots may have exterminated (almost) all alien life in the galaxy. This is motivated by the first law of robotics - they must protect humans from harm, but are not required to place value on any other form of life. They have covered up their actions, to protect humans from having to feel bad about it.
This would explain the disappearance of the Jovians.
Foundations's Fears was authorized by the Asimov estate after his death. You may or may not consider it canon.
