How to Sign Message in Bitcoin Electrum:
https://www.altcointrading.net/howto/sign-verify-message/#how-to-sign-a-message-in-electrum

If you're using a cold wallet, most of them provide their own signature guides.

Trezor:

https://trezor.io/learn/a/sign-verify?srsltid=AfmBOoqosBaEMg__ltExJv6U46MPlMoeCdb4DCXQe_O6het3Bo2QDBOH



Coldcard:

https://coldcard.com/docs/sign-text-file/

Ledger:
https://support.ledger.com/article/16056574709021-zd