The Necklace is now inhabited by four peoples, three of them from Earth originally.
Los Carnivales were the first Humans to arrive, almost 500 years ago. They came from Earth on the Brazilian Slowboat Carnivale, and they had left the Earth just before the cut off point between survival and death. Their ship was slapped together in a rush, and was consequently a bit shoddier than most slowboats, but it was faster, and passed the slower ships en route to become one of the first to reach haven in the Cluster.
Unfortunately, the Carnivale broke up on entering the denser air of the Necklace, and chunks of the ship landed in different places along The River. With only the scraps of ship and little technology, their culture crashed down to a very low level in a short time. During that time, the Carnivales were trained by rote in their duties to maintain what scraps of tech they had. This led to several ritual clans spread throughout the scattered tribes, who ritually memorize practices like programming, hydroponics, tending a fusion reactor, mechanics, and the like, which they have no real ability to exploit, but they try to adapt to local materials.
Most Carnivales live in tribes scattered along the river, and maintain at best a Tech Level 4 (Renaissance) life. A few live in cities and towns of the Altisherpas and Rasi, and have adapted to the higher tech levels of these cultures.
Next to hit the Necklace was the UN Slowboat Achilles, some 400 years ago, with a crew of Sherpas, Canadians, Swiss, Fililipinos, and Columbians. Achilies entered into the Necklas and settled in The River, forming an island. The children were bred to be resistant to zeroG - with enhanced calcium retention, larger lungs, and foot-hands. They are called "Altisherpas". They are explorers and able to live anywhere in the torus. The Achilles is now the largest city in the Torus, and site of a starport.
The Altisherpas maintain a fixation on biology, medicine, and genetics - reaching to TL 10 in those areas, but maintain a TL 8 in all other aspects. they travel the Necklace in fusion powered jet craft, and settle wherever they like, as they have no need for gravity.
The last major Human settlement was 150 years ago from the UN Slowboat "Ras Al-Khaimah" - Built by the UAE and gifted to the UN, crew included Icelanders, Koreans, New Zealanders, UK citizens, UAE Arabs, and Malians. They were forced to settle in the Torus as the good real estate - the two icy water worlds in the outer system - had already been claimed. Its people are called the Rasi, and are settled in a city made from their ship, and many towns along The River.
The Rasi are closer to standard Cluster Humans than the others, being more recently come and less adapted. They maintain a culture that varies from TL 9 in their capital to TL 7 in their smaller towns. They are fairly tightly bunched, with towns sometimes less than 100 km apart. They make their own grav plates and use them to graviform asteroids which have no appreciable gravity.
The fourth people are aliens. We haven't created them yet, but they live on the gas giant core, and are not the Builders. They evolved after the Builders left.