I've got Webmin 1.8.4.1 installed on Ubuntu 19.10 running MariaDB 10.3.2.2-MariaDB-0ubuntu0.12.10.1 I've gone into Webmin > Servers > MySQL -> Settings and set the Password Hashing mode to "Old". Saved Settings and attempted to create a new user. Failed to save user : SQL set password for 'test'@'%' = 'test' failed : Password hash should be a 41-digit hexadecimal number. So, perhaps it didn't save the settings?