There is a theory he was from the Greek island of Chios.
"In 1982, Ruth Durlacher hypothesised that Chios was Christopher Columbus's birthplace.[64] Columbus himself said he was from the Republic of Genoa, which included the island of Chios at the time. Columbus was friendly with a number of Chian Genoese families, referenced Chios in his writings and used the Greek language for some of his notes.[65] 'Columbus' remains a common surname on Chios. Other common Greek spellings are: Kouloumbis and Couloumbis."
"A New Theory Clarifying the Identity OF Christopher Columbus: A Byzantine Prince from Chios, Greece. by Ruth G Durlacher-Wolper 1982(Published by The New World Museum, San Salvador, Bahamas"
"In 1982, Ruth Durlacher hypothesised that Chios was Christopher Columbus's birthplace.[64] Columbus himself said he was from the Republic of Genoa, which included the island of Chios at the time. Columbus was friendly with a number of Chian Genoese families, referenced Chios in his writings and used the Greek language for some of his notes.[65] 'Columbus' remains a common surname on Chios. Other common Greek spellings are: Kouloumbis and Couloumbis."
https://en.m.wikipedia.org/wiki/Chios
"A New Theory Clarifying the Identity OF Christopher Columbus: A Byzantine Prince from Chios, Greece. by Ruth G Durlacher-Wolper 1982(Published by The New World Museum, San Salvador, Bahamas"
https://www.geraceresearchcentre.com/pdfs/1stColumbus/13_Dur...