Coins, Leagues, the War Trade Room and search show one chain at a time. Use the chain buttons to pick BNB, Solana or Robinhood. Your choice is remembered. A coin page always opens on the coin's own chain.
For a trade, your wallet must be on the coin's network. BNB Chain and Robinhood Chain use the same EVM address, so the wallet only needs to switch network. Solana needs a Solana wallet.