SMB Mounting problem with german Umlauts

I am switching several Computers from Windows to Ubuntu 20.04 and have a problem with a very, very old SMB Server i have to connect to. That Server is running Samba V2.2.5 and is configured to use ISO8859-15 as a charset for all files and drives on this server. I cannot change the configuration of that server because several windows clients are connecting to it.

After several days of try&error i managed to mount that SMB share on my Ubuntu 20.04 client with the following command:

sudo smbmount //192.168.224.16/jw /mnt -o username=jw,sec=ntlm,vers=1.0,uid=1000,gid=1000,nounix

Yes, i know sec=ntlm is really, really obsolete, and yes, i know vers=1.0 is really, really obsolete, too. Nevertheless this is the only protocol combination i found out to work connecting to this ancient server.

The only problem left is the conversion of german Umlauts in Filenames. If i ls a directory on that server it looks like:

drwxr-xr-x 2 jochen jochen 0 Mai 10  2015  .
drwxr-xr-x 2 jochen jochen 0 Sep 30 16:32  ..
drwxr-xr-x 2 jochen jochen 0 Jul  1  2020  W007D_Dokumente
drwxr-xr-x 2 jochen jochen 0 Mär 21  2020  W007L_Leiterplatten
drwxr-xr-x 2 jochen jochen 0 Feb 19  2015  W007S_Software
drwxr-xr-x 2 jochen jochen 0 Mär 21  2020 'W007Z_Zusammenf'$'\201''gungen'

The last directory should be "W007Z_Zusammenfügungen". I tried several "iocharset="-Options when mounting - no difference at all. I tried "codepage="-Options when mounting - seems to be obsolete and not used any longer.

locale on the Ubuntu client shows:

jochen@HP8510W-3:~$ locale
LANG=de_DE.UTF-8
LANGUAGE=de_DE:en
LC_CTYPE="de_DE.UTF-8"
LC_NUMERIC=de_DE.UTF-8
LC_TIME=de_DE.UTF-8
LC_COLLATE="de_DE.UTF-8"
LC_MONETARY=de_DE.UTF-8
LC_MESSAGES="de_DE.UTF-8"
LC_PAPER=de_DE.UTF-8
LC_NAME=de_DE.UTF-8
LC_ADDRESS=de_DE.UTF-8
LC_TELEPHONE=de_DE.UTF-8
LC_MEASUREMENT=de_DE.UTF-8
LC_IDENTIFICATION=de_DE.UTF-8
LC_ALL=

Any ideas?

Thankful for all support i can get!

Some experimenting:

~/test$ touch W007Z_Zusammenfügungen
~/test$ convmv -f UTF-8 -t ISO_8859-15 W007Z_Zusammenfügungen --notest
~/test$ ls
'W007Z_Zusammenf'$'\374''gungen'

(I got '$'\374'' to represent ü, not '$'\201''.)

Then I took these steps:

1. Created the German ISO-8859-1 locale:

   ~/test$ sudo locale-gen de_DE
   Generating locales (this might take a while)...
     de_DE.ISO-8859-1... done
   Generation complete.
   

2. Changed the encoding in my gnome-terminal profile to Western — ISO-8859-15

And then:

~/test$ LC_CTYPE=de_DE ls
W007Z_Zusammenfügungen