Pessoal, só para complementar, a Electrum mantém compatibilidade com o formato WIF antigo.
Como podemos verificar no
release note:
* The Wallet Import Format (WIF) for private keys that was extended in 3.0
is changed. Keys in the previous format can be imported, compatibility
is maintained. Newly exported keys will be serialized as
"script_type:original_wif_format_key".
Fonte:
https://github.com/spesmilo/electrum/blob/master/RELEASE-NOTESVlw!