pure-ftpd-mysql doesnt start

after upgrading mariadb on Debian GNU/Linux 9.12 (stretch) (4.9.0-12-amd64) pureftp doesnt restart.
Logfile says

Code:

Apr  3 09:39:47 vcawws01 pure-ftpd-mysql[1632]: Starting ftp server: Running: /usr/sbin/pure-ftpd-mysql-virtualchroot -l mysql:/etc/pure-ftpd/db/mysql.conf -l pam -Y 1 -H -D -E -J HIGH -A -u 1000 -b -8 UTF-8 -O clf:/var/log/pure-ftpd/transfer.log -B
Apr  3 09:39:47 vcawws01 pure-ftpd-mysql[1632]: /usr/sbin/pure-ftpd-mysql-virtualchroot: relocation error: /usr/sbin/pure-ftpd-mysql-virtualchroot: symbol my_make_scrambled_password, version libmariadbclient_18 not defined in file libmariadbclient.so.18 with link time reference

Try to follow this guid: https://www.howtoforge.com/community/threads/debian-stretch-pureftp-newer-mariadb-fixes.79514/
But got error when running

Code:

dpkg -i pure-ftpd-mysql_1.0.43-3.1_amd64.deb pure-ftpd-common_1.0.43-3.1_all.deb

Code:

pure-ftpd kollidiert mit ftp-server
pure-ftpd-mysql liefert ftp-server und ist vorhanden und installiert.

 

What shows commands

Code:

apt-cache policy mariadb-server

apt-cache policy mariadb-client

 

Code:

mariadb-server:
  Installiert:           1:10.4.12+maria~stretch
  Installationskandidat: 1:10.4.12+maria~stretch
  Versionstabelle:
 *** 1:10.4.12+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
        100 /var/lib/dpkg/status
     1:10.4.11+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
     1:10.4.10+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
     10.1.44-0+deb9u1 500
        500 http://ftp.de.debian.org/debian oldstable/main amd64 Packages
     10.1.37-0+deb9u1 500
        500 http://security.debian.org oldstable/updates/main amd64 Packages

Code:

mariadb-client:
  Installiert:           1:10.4.12+maria~stretch
  Installationskandidat: 1:10.4.12+maria~stretch
  Versionstabelle:
 *** 1:10.4.12+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
        100 /var/lib/dpkg/status
     1:10.4.11+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
     1:10.4.10+maria~stretch 1000
       1000 http://downloads.mariadb.com/MariaDB/mariadb-10.4/repo/debian stretch/main amd64 Packages
     10.1.44-0+deb9u1 500
        500 http://ftp.de.debian.org/debian oldstable/main amd64 Packages
     10.1.37-0+deb9u1 500
        500 http://security.debian.org oldstable/updates/main amd64 Packages

 

The guide you refer to installs Mariadb 10.3, you have now 10.4. It may just not work.
But to resolve the immediate error, you could try

Code:

apt-get remove pure-ftpd-mysql

and then try again dpkg --install. That may or may not help.
Since you are installing extra repositories, I assume you do have a reason for doing so and dealing with the associated incompatibility and maintenance problems.