The most accurate response to the question about what results from eukaryotes coming about due to endosymbiosis is: ancient prokaryotes living inside of modern eukaryotes.
Endosymbiosis theory suggests that eukaryotic cells originated through a process in which certain prokaryotic cells engulfed other prokaryotic cells, leading to a symbiotic relationship. Over time, these engulfed prokaryotes (like mitochondria and chloroplasts) became integral parts of eukaryotic cells, retaining some of their own DNA, but functioning within the host cell.