[Samba] a way to migrate pasword from Samba 4.0 AD DC to new AD DC?

[Franta Hanzlík]

Please, is there any way to migrate passwords from old Samba 4.0 Ad DC
to new (Samba 4.20) one?
On ldbsearch export on old AD only related item I see is 'unicodePwd'
attribute, and it is maybe possible write to new system using ldbmodify
 - but it is right and simplest solution?

And one more question - why don't I get any result from the command
(on 4.20 AD DC, provisioned with --plaintext-secrets):

# samba-tool user getpassword testusr --attributes=unicodePwd,virtualClearTextUTF16,virtualClearTextUTF8
on: CN=testusr,OU=users,DC=ad,DC=my,DC=home
unicodePwd:: CkODmLSx+ZaJO/qHDQibNw==
Got password OK

Why are the virtualClearTextUTF16 and virtualClearTextUTF8 values ​​
missing and how do I make them exist?
Does using the 'samba-tool user syncpasswords' command have anything 
to do with this?
-- 
Thanks in advance, Franta Hanzlík