This repo still exists in archived form, but the maintained version has now relocated to: https://github.com/Mythic-Project/governance-ui
You can set custom URLs via the configuration for any self-hosted Jupiter APIs, like the V6 Swap API or Paid Hosted APIs Here is an example:
NEXT_PUBLIC_JUPTER_SWAP_API_ENDPOINT=https://quote-api.jup.ag/v6