Why do my 'sign message' not work on Bitcoin core If I choose a freshly generated address in Core, and I then choose to sign a message with it, it returns the error message "The entered address does not refer to a key".

Why is this? There should definitely be a key considering that it's an address generated by my seed. It is also the correct address as I checked it multiple times.
Addresses that start with bc1, called Bech32 addresses, can't be used to sign messages, at least for now. It might change in the future.