Here's what I don't like. Nothing living appears on Europa's surface. In the same 4.5 billion years, Earth went from single-cell life to whales, jungles, and humans.
It is also extremely cold (-171C mean) and near-vacuum (100 nanopascal).
If there is life in Europa and it bears any resemblance whatsoever to the biology we know, it simply couldn't exist on the surface. Even the hardiest single-celled organisms here, which have also had 4.5B years to evolve into uncontested niches, could barely survive a limited exposure to these factors.
I do assume this extreme level of cold and vacuum can also be acclimated in those 4.x billion years
I'd be ecstatic to be proven wrong empirically, but it doesn't make sense to start our search there.
https://en.wikipedia.org/wiki/Sievert#Dose_examples
5–10 μSv: One set of dental radiographs
10–30 mSv: Single full-body CT scan
80 mSv: 6-month stay on the International Space Station
1 Sv: Maximum allowed radiation exposure for NASA astronauts over their career
5 Sv: Calculated dose from the neutron and gamma ray flash, 1.2 km from ground zero of the Little Boy fission bomb, air burst at 600 m
5.1 Sv: Fatal acute dose to Harry Daghlian in 1945 criticality accident
He died 25 days later
54 Sv: Fatal acute dose to Boris Korchilov in 1961 after a reactor cooling system failed on the Soviet submarine K-19 which required work in the reactor with no shielding
He died 6 days later