Although I also found this site
https://reinproject.org/bitcoin-signature-tool/#sign, which I can use to sign and verify messages, after signing the message and trying to verify it, the Bitcoin wallet address has again changed to the first one from the Ian Coleman site.
You may want to change your wallet and discard your seed since you seem to have entered it into so many online websites so far. When you do things like this, there is a chance that you leak your keys!
As for the website you shared, it doesn't seem to be using a deterministic algorithm to generate the ephemeral key needed for creating an ECDSA signature which could be a source of some possible vulnerabilities. For example if it uses a weak key, after you share the signed message + signature your private key could be leaked.
This is why you should always try to stick to popular wallets that are well tested and reviewed not any random tool you find on the internet.