Bitcoin Signature ≠ Lightning Network
Signing a Bitcoin message proves that you are indeed the owner of a BTC address.
This has nothing to do with Lightning, which is a system for making fast and inexpensive payments.
You can sign a message with a regular Bitcoin address without ever using Lightning.
Your mistake stemmed from using Electrum in Lightning mode, which confused you.
Lightning Wallets vs. Regular Bitcoin Wallets
Apps like Muun, Blink SV, or Bitget Wallet are designed to make Lightning incredibly simple.
But they cannot sign a message with a regular Bitcoin address.
To sign a message, you need wallets like Electrum, Bitcoin Core, Ledger, Trezor, or sometimes Trust Wallet.
Why a BTC Balance?
The website (koinvote) wants to verify that your address is not empty, that it is "active."
So it requires you to have at least a few satoshis (the smallest unit of Bitcoin).
But be aware: the signature itself remains a normal Bitcoin function, not Lightning.
In summary:
Signing a message = proving that you control a Bitcoin address.
Lightning = a fast payment system, but not necessary for signing.
Some wallets can sign, others cannot.
The site simply wants to ensure that your address contains some Bitcoin to be valid.