I can't connect to ssh because of the error mentioned in the title. I found on other sources that i had to modify the file ~/.ssh/authorized_keys, but the folder is empty, and creating the file didn't changed anything.
To use SSH key authentication you need to add your public key to /storage/.ssh/authorized_keys before disabling password access in the LE settings add-on. Note that disabling SSH password auth does not stop the SSH daemon from prompting for passwords; but it does guarantee that no password will be accepted.