WERR_UNKNOWN_PRINTER_DRIVER after a good cupsaddsmb printer driver installation.
Also happens on prior versions of Samba.

Here's the whole output set with -d 3:

added interface ip=192.168.160.140
bcast=192.168.160.255 nmask=255.255.255.0
Connecting to host=printproc share=IPC$
Connecting to 127.0.0.1 at port 445
Doing spnego session setup (blob length=58)
got OID=1 3 6 1 4 1 311 2 2 10
got principal=NONE
Got challenge flags:
Got NTLMSSP neg_flags=0x20830205
NTLMSSP: Set final flags:
Got NTLMSSP neg_flags=0x20000205
lsa_io_sec_qos: length c does not match size 8

[Windows NT x86]
Printer Driver Info 3:
	Version: [2]
	Driver Name: [Canon]
	Architecture: [Windows NT x86]
	Driver Path:
[\\printproc\print$\W32X86\2\cupsdrvr.dll]
	Datafile: [\\printproc\print$\W32X86\2\Canon.ppd]
	Configfile: [\\printproc\print$\W32X86\2\cupsui.dll]
	Helpfile: [\\printproc\print$\W32X86\2\cups.hlp]


	Monitorname: []
	Defaultdatatype: [RAW]

result was WERR_UNKNOWN_PRINTER_DRIVER