And yet from the first prokaryotes until the first eukaryotes, a huge huge huge time gap.

As far as we know that evolution from prokaryote to eukaryote type organisms has only happened on our planet once (that we know of.) Whereas we know of two different types of single cellular organisms (bacteria and archaea)

We might find simple single-cell type life is quite ubiquitous in the cosmos. But what we think of most as life -- sexual reproduction, multicellular organisms, etc.... might be very infrequent.