I tried it now and got the same error. I think it's not a rights problem, because BUILTIN\Administrators has the needed privilege and admin is member of domain admins and domain admins is member of BUILTIN\Administrators:
[root@server ~]# net rpc rights list privileges SePrintOperatorPrivilege -U admin
Enter admin's password:
I tried to add printer drivers via print management from a Windows 10 client as described here:
I can write to \\server\print$ but access denied, when trying to add a print driver or printer.
Printing works with client side drivers. Does anybody know how add print drivers to the samba server, so clients may download them when needed?