If you are a steam user, you can also pass it as steam start parameter by writing “gfx_backend Vulkan” (INCLUDING the “) (rightclick ddnet in steam, properties -> start arguments
For non-Steam version you can edit the %appdata%\DDNet\settings_ddnet.cfg or %appdata%\Teeworlds\settings_ddnet.cfg and add a line with gfx_backend Vulkan, then start client.
Jupstar ✪
For non-Steam version you can edit the %appdata%\DDNet\settings_ddnet.cfg or %appdata%\Teeworlds\settings_ddnet.cfg and add a line with gfx_backend Vulkan, then start client.