You can easily have a seed phrase generating same p2wpkh-p2sh addresses in Electrum and iancoleman without any need to change the source code. (Maybe I am missing something?)
Go to iancoleman. Select BIP49.
https://i.imgur.com/q09RZiG.jpgGenerate a seed. iancoleman will give you some p2wpkh-p2sh addresses.
Then go to Electrum. Create a new wallet. Select "Standard Wallet" and then "I already have a seed". Enter the seed phrase generated by iancoleman. Don't forget to click on "options" and check "BIP39".
Click on "next" and select "p2wpkh-p2sh" as the "script type". Electrum will give you same addresses.
Yep in this direction it's working properly for me too, Seed generated by Iancoleman shows same addresses when entered in Electrum.
But a seed generated by Electrum (non standard mnemonic) entered in iancoleman dosen't show the same addresses.
The source code edit is needed because the tool will give "Invalid mnemonic" error if we try to put in the Electrum generated seed.
