Question: What community were the founding members of Islander 23's rival gang from?

Context paragraphs:
Trinity Ordona: Rev. Trinity Ordoña is a lesbian Filipino-American college teacher, activist, community organizer, and ordained minister currently residing in the San Francisco Bay Area.  She is notable for her grassroots work on intersectional social justice.  Her activism includes issues of voice and visibility for Asian/Pacific gay, lesbian, bisexual, transgender and queer individuals and their families, Lesbians of color, and survivors of sexual abuse.  Her works include her dissertation "Coming Out Together: an ethnohistory of the Asian and Pacific Islander queer women’s and transgendered people’s movement of San Francisco," as well as various interviews and articles published in anthologies like "Filipino Americans: Transformation and Identity" and "Asian/Pacific Islander American Women: A Historical Anthology".  She co-founded Asian and Pacific Islander Family Pride (APIFP), which "[sustains] support networks for API families with members who are LGBTQ," founded Healing for Change, “a CCSF student organization that sponsors campus-community healing events directed to survivors of violence and abuse,” and is currently an instructor in the Lesbian, Gay, Bisexual and Transgender Studies Department at City College of San Francisco.

Alex García (boxer): Alex García (born December 2, 1961) is a Mexican-American and former heavyweight boxer best known to be a contender in the 1990s.  A San Fernando native, and former gang member, he served five years in San Quentin State Prison for stabbing a rival gang member.  Upon his release, he found himself training at the Jet Center, where he took up boxing.  He was mentored under William “Blinky” Rodriguez.

Apex (gang): Apex is a street gang in Melbourne, Australia.  It was formed in 2012.  The founding members were part of Victoria's South Sudanese community, although the gang later became more diverse, particularly after it merged with the YCW gang.  Associated with violent car-jackings and burglaries, Apex came to prominence in the national media after a brawl in Melbourne's Central Business District between it and the rival Islander 23 gang in March 2016 after the Moomba parade.  This prompted a crackdown by Victoria Police.  They apparently have little structure and no official colours.

Altamira prison brawl: The Altamira prison brawl was a deadly fight that occurred on 4 January 2012 in Altamira, Tamaulipas, Mexico.  Officials from the state of Tamaulipas confirmed that 31 people were killed, with another thirteen injured.  The fight started after a drug gang burst into a section of the prison where they were banned from, attacking their rival gang housed there, triggering the fight.  During the altercation, the inmates used several kinds of white arms to kill their opponents.  The prisoners also used sticks and knives to massacre the members of the rival gang.

Myles O'Donnell: Myles O'Donnell was an Irish American bootlegger and mobster during the Roaring Twenties in Chicago during Prohibition.  He was most famous for being the founder of the West-side O'Donnell Mob aka the Westside O'Donnells or West-side gang (no relation to the South Side O'Donnells, a rival gang).

Vito Bonventre: Vito Bonventre (January 1, 1875 – July 15, 1930) was a New York City mobster who was a leading member of the Brooklyn gang that would later become the Bonanno Crime Family.  He was arrested but then released in 1921 as the leader of a group known as the "Good Killers."  Bonventre was murdered in 1930 at the start of a conflict between his gang and a rival gang led by Joe Masseria, referred to as the Castellammarese War.

Manya Surve: Manohar Arjun Surve (8 August 1944  – 11 January 1982), popularly known as Manya Surve, was one of the dons who made an impact in the Mumbai underworld.  He was adarsh singh's chela Being a Hindu, he was denied just two years, his gang rose to such prominence that Pathans, who ruled the underworld for over two decades, sought his help to eliminate the leader of their arch rival gang, the Konkani speaking Kaskar group.  It was headed by Dawood Ibrahim's elder brother, Sabir.  Manya was known for his dare devilry and strategic planning.  For Manya, it was a clear shot to success.  The top gang of the city had come asking him for help and in doing so he would eliminate the other.  The first educated Hindu gangster, who hailed from an area called Agar Bazaar in the suburbs of Dadar.  Manohar Surve, a young man, fresh Kirti College got implicated in a murder that he did not commit and was sentenced to life in Yerwada Jail.

2013 Palmasola prison riot: On August 23, 2013, a prison riot broke out at Palmasola, a maximum-security prison in Santa Cruz, Bolivia.  The riot started when members of one cell block attacked a rival gang in another, using propane tanks as flame throwers.  Thirty-one people were killed, including an 18-month-old child who was living at the prison.  Thirty-seven others were seriously injured.  The riot led to calls for reform in the Bolivian prison system, which is plagued by overcrowding and long delays in the trial system.

Richie Fitzpatrick: Richard "Richie" Fitzpatrick (1880 – November 1, 1904) was a top gunman in the Monk Eastman gang, as well as a former member of the Five Points Gang, during the late 1890s until his death in 1904.  He is best known however for the method of eliminating an Eastman rival where he would meet with the person in question and, after being searched, would inform them that he would not follow Eastman's orders instead seeking to defect to the rival gang and as he excused himself to use the bathroom he would retrieve a planted gun and return surprising the person shooting the victim down.  This would later inspire the famous scene in "The Godfather" Saga.

Islander 23: Islander 23 also known as I-23 is a Pacific Islander street gang in West Melbourne, Victoria, Australia.  Islander 23 came to prominence in the national media after a large scale brawl in Melbourne's Central Business District between it and the rival gang Apex in March 2016 after the Moomba parade.  It consists largely of youths from a South Pacific background.

Supporting paragraphs: Islander 23 Apex (gang)
Answer: Victoria's South Sudanese community