chainId parameter (1 or 4663).
Ethereum mainnet (chainId 1)
Robinhood Chain (chainId 4663)
Robinhood Chain is an Arbitrum-stack L2 with ETH as the gas token. The block explorer is Blockscout; markets there are denominated in USDG (Global Dollar) rather than USDC.
UserProxy contracts are not listed here. One is deployed per position as an EIP-1167 minimal clone at the time you open it, so its address is specific to your position — read it from the
userProxy field on the position.