I've faced with same problem on following configuration:

> $ glxinfo  | grep Device
>     Device: AMD JUNIPER (DRM 2.50.0 / 4.18.0-15-generic, LLVM 7.0.0) (0x68ba)
> $ glxinfo | grep 'OpenGL version string'
> OpenGL version string: 3.1 Mesa 18.3.3
> $ lspci | grep 'VGA.*Radeon'
> 01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Juniper XT [Radeon HD 6770]
> $ lspci -vv -s 01:00.0 | grep driver
> 	Kernel driver in use: radeon
> $ . /etc/lsb-release ; echo $DISTRIB_DESCRIPTION
> Ubuntu 18.04.2 LTS
> $ uname -a
> Linux ivanhome 4.18.0-15-generic #16~18.04.1-Ubuntu SMP Thu Feb 7 14:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux