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That's the thing: a staked address is meant to prove you're the long-term account owner. Your account is over 10 years old, your staked address was only a few years old.
I never used them anyway. I mainly created and staked them for testing purposes.Quote
Staking a new one is exactly what an account buyer/hacker would do, it means you can no longer prove you're the long-term owner.
Account buyers/hackers might buy/hack accounts but it's not usual for them to buy/hack bitcoin private keys...Quote
You're going to be disappointed: there is no "standard" for signing messages from Segwit addresses. Electrum came up with something, but Bitcoin Core can't even do it.
Don't worry about it. Electrum will do just fine! Others will follow in the future... 