Radeon HD 6990 GPU
I got an old Radeon HD 6990 GPU.
Is it possible that this card unsupported by hashcat?
Its a hybrid system. I have installed 2 nVidia GPUs. These are working correctly.

freeroute@Vanda:~$ lsb_release -a
LSB Version: core-9.20170808ubuntu1-noarchConfusedecurity-9.20170808ubuntu1-noarch
Distributor ID: Ubuntu
Description: Ubuntu 18.04.3 LTS
Release: 18.04
Codename: bionic

uname -a
Linux Vanda 5.0.0-27-generic #28~18.04.1-Ubuntu SMP Thu Aug 22 03:00:32 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

I tried to install driver by this instruction: https://github.com/RadeonOpenCompute/ROCm

Thank you for your support.
6990 is way too old for rocm
Ahh. Thanks the info.