One phrase on one piece of paper, covering every chain you are likely to hold.
Solana keypairs are ed25519, derived per SLIP-0010 at m/44'/501'/0'/0' — the same path Phantom and the Solana CLI use, so the address you write down is the address those wallets will show you when you restore.
You can derive multiple Solana accounts from one seed by incrementing the account index, exactly as any standard wallet does.
secp256k1, native SegWit by default at m/84'/0'/0'. Legacy and nested SegWit paths are shown as well, for restoring into older software.
One address covers Ethereum, Base, Arbitrum, Optimism, Polygon and every other EVM network, because they share an address format. Derived at m/44'/60'/0'/0/0.
All of these come from the same BIP-39 phrase. Write down twelve or twenty-four words once and you have written down every chain at the same time. Losing the paper loses all of them — which is worth sitting with before you decide where to keep it.