Your server has mariadb installed, which needs to be deleted before it can be used normally. Is this installed by you yourself or comes with the system?
If it is useless, it can be deleted. Then start mysql. If it still doesn't work, it is recommended to reinstall mysql. Please take a system snapshot before the operation.
apt remove mariadb*
cd /etc/systemd/system/
rm mysqld.service mysql.service
systemctl daemon-reload
/etc/init.d/mysqld start
ranaset6