Server does not support diffie-hellman-group1-sha1 for keyexchange

Add the following to /etc/ssh/sshd_conf while logged in as root (same password as Admin if you are on a Synology NAS)
 

KexAlgorithms diffie-hellman-group1-sha1,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1 Ciphers 3des-cbc,blowfish-cbc,aes128-cbc,aes128-ctr,aes256-ctr

After adding these, run "ssh-keygen -A" to make it generate the keys not needed before the changes, and restart the SSHd service on the machine (reboot works fine, too) 

source: https://www.veeam.com/kb2061

mysql (mariadb) ERROR 1698 (28000): Access denied for user 'root'@'localhost'

sudo mysql -u root
use mysql;
update user set plugin='' where User='root';
flush privileges;
exit;

source: http://superuser.com/a/1077144/509195