Problem has gone with Mesa 19.0 (I've checked on OpenSUSE Tumbleweed):

> $ glxinfo  | grep Device
    Device: AMD JUNIPER (DRM 2.50.0 / 5.0.3-1-default, LLVM 7.0.1) (0x68ba)
> $ glxinfo | grep 'OpenGL version string'
OpenGL version string: 3.1 Mesa 19.0.0
> $ /sbin/lspci | grep 'VGA.*Radeon'
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Juniper XT [Radeon HD 6770]
> $ /sbin/lspci -vv -s 01:00.0 | grep driver
        Kernel driver in use: radeon
> $ cat /etc/os-release 
NAME="openSUSE Tumbleweed"
# VERSION="20190327"
ID="opensuse-tumbleweed"
ID_LIKE="opensuse suse"
VERSION_ID="20190327"
PRETTY_NAME="openSUSE Tumbleweed"
ANSI_COLOR="0;32"
CPE_NAME="cpe:/o:opensuse:tumbleweed:20190327"
BUG_REPORT_URL="https://bugs.opensuse.org"
HOME_URL="https://www.opensuse.org/"
> $ uname -a
Linux ivanhome 5.0.3-1-default #1 SMP Fri Mar 22 17:30:35 UTC 2019 (2a31831)
x86_64 x86_64 x86_64 GNU/Linux