Okay thanks @kanhu and @Aleks it works
Resume
Clear MySQL with
- mv /var/lib/mysql
- apt-get install --reinstall mariadb-server
- yunohost tools regen-conf -f mysql
- yunohost service restart mysql
- get password from `cat /etc/yunohost/mysql``
# reset password
GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' IDENTIFIED BY '<password>';
# first (not sure it was useful)
UPDATE user SET plugin='mysql_native_password' WHERE User='root';
# then
UPDATE mysql.user SET Grant_priv='Y', Super_priv='Y' WHERE User='root';
FLUSH PRIVILEGES;
GRANT ALL ON *.* TO 'root'@'localhost';
# then
mysql restart