To comply with Ledger Live Clear Signing, max chainID is not MAX_SAFE_CHAIN_ID as we today have but rather 4 bytes.
Impact of having >4bytes chainID (told by Ledger Team):
you'd be able to sign your transactions just fine, but providing metadata to the device for like decoding the calldata and displaying informations using things like tickers, decimals etc, all of that is signed by ledger, and the whole signature scheme assumed that a chainId is max 4 bytes
To comply with Ledger Live Clear Signing, max chainID is not MAX_SAFE_CHAIN_ID as we today have but rather 4 bytes.
Impact of having >4bytes chainID (told by Ledger Team):
Documentation of the Ethereum app here: https://github.com/LedgerHQ/app-ethereum/blob/develop/doc/ethapp.adoc ERC20 example:
Context: ChainIDs ~20 networks today are higher than 4B, out of like the ~2000 you can find on chainlist