That is the case. Receive Bitcoin. The app I'm buying from is asking me to sign a message so that it can confirm I'm actually the owner of that address!
This is just my opinion, I think you can also wait for the opinion of others. You can do this offline, not make the Electrum wallet sychronize with the blockchain:
If you are able to the export/see the private key (child private key, not master private key), of the address you use for purchase, you can import it on Electrum, sign a message with the address on Electrum. Use Tor.
After you have successfully done that and successfully make the purchase, you can delete the Electrum wallet.
Well, thing is that I didn't want to expose the priv key to the internet. I create these addresses in offline nodes so that the priv keys never "sees" the internet!
If I don't have another way, I'll do that, and then, I will create a fresh new address in my offline node and transfer the Bitcoin there!
