The thing about Electrum seed phrases is that their major difference is in how the seed phrase itself is generated, and not in how the seed phrase is used to generate private keys. Just like BIP39 phrases, they still get paired with a salt using any additional passphrase (if one is set), they still go through 2048 rounds of HMAC-SHA512, they still generate a 512 bit seed number, and they still derive private and public keys in the same hierarchical manner. Literally the only difference is they use the word "electrum" instead of the word "mnemonic" in the salt, and they use a different derivation path. Therefore, any open source BIP39 wallet or code (such as Ian Coleman's site) can be changed pretty trivially to accept Electrum phrases and generate the same addresses as Electrum itself would.