BGK
You basically get it from /var/lib/tor/
Do be aware that if you use push notifications in BlueWallet, your transaction info will still be sent to the devs' servers, who then push notifications about confirmations and such, to Google / Apple servers, which finally deliver the notification to your phone. Kind of defeats the purpose to use a private Electrum server.
Unless you host the push notification service yourself, too; it's called Ground Control, but I haven't tried it as I don't use this wallet.