I find out that you acually can.
yes, right..
to have segwit addresses starting with a 3 in Electrum just follow these simple steps:
1) generate a bip39, 12 words seed on
https://iancoleman.io/bip39/ (use it offline for more security)
2) on electrum choose, File -> New/Restore -> Standard Wallet -> I already have a seed -> click on "options" and choose bip39, write the seed then click next
3) on derivation path path use:
m/49'/0'/0'/0that's all. Remember to save in a safe place the seed as electrum will not show it (read below)