Segwit addresses are not derived from legacy addresses. However a legacy address can be derived from a private key for a segwit address, and vice versa. Private keys are just numbers and are not locked to a specific type of address that they should be used to create.
Note that Electrum uses a special format for private keys in order to indicate what type of address they should be used for. You will need to export those private keys and convert them into a format that your forked coin's wallet can understand.
Thank you appreciate your insight.
So the question is, do you know how to convert the exported Electrum key?
Base58check-decode the WIF private key, change the version byte from 0x81 (for Bech32 P2WPKH) or 0x82 (for P2WPKH nested in P2SH) to 0x80 (or whatever your fork coin uses), then base58check-encode the result. Note that I am only describing the conversion of the WIF. I make no statement whatsoever about what may or may not work for attempts to claim forked coins.
Here is the full set of values Electrum uses, copied from the source of some unreleased software of mine:
/*
* From Electrum 3.0 Release Notes
* https://github.com/spesmilo/electrum/blob/2774126db6c258807d95921936eb13af07047d97/RELEASE-NOTES
*/
#define WIF_P2PKH 0x80
#define WIF_P2WPKH 0x81
#define WIF_P2WPKH_P2SH 0x82
#define WIF_P2SH 0x85
#define WIF_P2WSH 0x86
#define WIF_P2WSH_P2SH 0x87
Do you know any programming, or do you need a tool for this?
