我的GPU是NVIDIA GeForce GT 705。运行./UE4Editor时，出现错误： "Cannot find a compatibe Vulkan device or driver"（无法找到兼容的Vulkan设备或驱动程序）。因此，我尝试按照这个页面在Linux上安装和测试Vulkan来安装Vulkan。 sudo add-apt-repository ppa:graphics-drivers/ppa和sudo apt升级可能是正确的。
$ sudo ubuntu-drivers devices
== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd0000104Csv00001028sd0000109Bbc03sc00i00
vendor : NVIDIA Corporation
model : GF119 [GeForce GT 705]
driver : nvidia-340 - distro non-free
driver : nvidia-driver-390 - distro non-free recommended
driver : xserver-xorg-video-nouveau - distro free builtin
$ sudo add-apt-repository ppa:graphics-drivers/ppa
Hit:1 http://jp.archive.ubuntu.com/ubuntu focal InRelease
Get:2 http://jp.archive.ubuntu.com/ubuntu focal-updates InRelease [107 kB]
Get:3 http://jp.archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB]
Hit:4 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu focal InRelease
Get:5 http://security.ubuntu.com/ubuntu focal-security InRelease [107 kB]
Get:6 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal InRelease [23.8 kB]
Get:7 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal/main amd64 Packages [7,196 B]
Get:8 http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu focal/main i386 Packages [6,924 B]
Fetched 350 kB in 3s (128 kB/s)
Reading package lists... Done
但是，以下是错误信息。
$ sudo apt install nvidia-graphics-drivers-396 nvidia-settings vulkan vulkan-utils
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package nvidia-graphics-drivers-396
E: Unable to locate package vulkan
我不知道为什么nvidia-graphics-drivers-396和vulkan不存在，也不知道如何安装vulkan。请告诉我。