Source: cirosantilli/there-are-no-known-eukaryotes-which-never-had-mitochondria
= There are no known eukaryotes which never had mitochondria
As of 2020, there are no known <eukaryotes without mitochondria>[eukaryotes which have never had mitochondria].
Known <eukaryotes without mitochondria>, which are very rare, have lost mitochondria they previously had.
Having mitochondria appears to be a requisite for being an eukaryote. This is one of the central thesis of <Power, Sex, Suicide by Nick Lane (2006)>.