The "sweep" dialog in Electrum will actually allow you to send to ANY Bitcoin address that you like... it defaults to one in the current wallet... but you can change it to any address you want.
So, if you select "standard wallet -> use a hardware device"... and connect up the Ledger, it will generate a copy of the ledger wallet. If you use a derivation path of m/44'/0'/0' (the default setting), it will recreate your Ledger "Legacy" wallet... if you use a derivation path of m/49'/0'/0' if will recreate your Ledger "SegWit" wallet.
Once you have created the wallet you want, "Wallet -> Private Keys -> Sweep" and then you can simply sweep to the Ledger address that you want.
Also, there is no "Segwit Blockchain" and no "Legacy Blockchain"... just different address types on
one Blockchain