There are some who says plasmids are found in some eukaryotes but is it like scientifically proven?
These resources may help.
This book, “Plasmids of Eukaryotes”, explains that...
“The possession of plasmids was for a long time recognized only in the bacteria. It is now evident that plasmids, or replicative forms of DNA structurally and experimentally comparable to bacterial plasmids, exist in eukaryotic organisms as well. Such plasmids are in fact common among fungi and higher plants.”
Also, this website (ScienceDirect) explains that...
“Most plasmids inhabit bacteria, and indeed around 50% of bacteria found in the wild contain one or more plasmids. Plasmids are also found in higher organisms such as yeast and fungi. The 2 micron circle of yeast (discussed later) is a well-known example that has been modified for use as a cloning vector.“