This is the vkBasalt flatpak.

In the documentation below, $APP_ID will be referred to the application ID. Steam's ID for example is com.valvesoftware.Steam, however this differs per application.

To temporarily enable vkBasalt on an application, run the following command:

flatpak run --env=ENABLE_VKBASALT=1 $APP_ID

To permanently enable vkBasalt on an application, run the following command:

flatpak override --env=ENABLE_VKBASALT=1 $APP_ID

You may have to add --user if the application in question was installed per user.

To enable vkBasalt per game on Steam, edit the launch option of a game and add:

ENABLE_VKBASALT=1 %command%

By default, games will utilize the vkBasalt configuration from config/vkBasalt.conf, which is located in /var/lib/flatpak/runtime/org.freedesktop.Platform.VulkanLayer.vkBasalt/[...]/active/files/etc/vkBasalt/vkBasalt.conf if installed for the system or $HOME/.local/share/flatpak/runtime/org.freedesktop.Platform.VulkanLayer.vkBasalt/[...]/active/files/etc/vkBasalt/vkBasalt.conf if installed per user.

You can create a custom vkBasalt.conf file at $HOME/.var/app/$APP_ID/config/vkBasalt, where games will utilize this configuration file instead:

mkdir $HOME/.var/app/$APP_ID/config/vkBasalt
curl https://raw.githubusercontent.com/DadSchoorse/vkBasalt/master/config/vkBasalt.conf -o $HOME/.var/app/$APP_ID/config/vkBasalt/vkBasalt.conf
$EDITOR $HOME/.var/app/$APP_ID/config/vkBasalt/vkBasalt.conf