I know it's a silly question, but did you check whether you have the Vulkan part of Mesa installed?

Yes, i have the mesa-vulkan-drivers package installed.

Is there a list somewhere about the supported cards by RADV? Maybe yours is not yet.

See if the command 'vulkaninfo' looks ok.
It should find your manifests from the VulkanSDK & the mesa installed *json files.
The are found in:
.../VulkanSDK/1.0.XX.X/x86_64/etc/explicit_layer.d/VkLayer_standard_validation.json
and from mesa
/usr/share/vulkan/icd.d/radeon_icd.x86_64.json
Next look for the extension under "Instance Extensions."
If you have some extensions going for you you are good.
It should say that RADV isn't yet a conforming
driver,assuming you are using a radeon card.

Next check under "Presentable Surfaces". The field "GPU"
should give tell you your vulkan presentation instance.
You can create a vulkan instance without presentation.
Hence, that means without a card supporting vulkan you'll
have to render off screen.
Mine says:
GPU id       : 0 (AMD RADV POLARIS11 (LLVM 4.0.1))

Next check the "VkPhysicalDeviceProperties".
Does it look like mine with POLARIS?
apiVersion     = 0x400039  (1.0.57)
driverVersion  = 71315458 (0x4403002)
vendorID       = 0x1002
deviceID       = 0x67ef
deviceType     = DISCRETE_GPU
deviceName     = AMD RADV POLARIS11 (LLVM 4.0.1)
If the fields aren't filled out then something is wrong.
Have you tried playing some vulkan games?

Thanks for both of the answers. I have a r9 270x, which is supported by vulkan according to AMD, have not found mesa source though.

Vulkaninfo doesn't work either, it exits with a 'VK_ERROR_INITIALIZATION_FAILED', even though it finds a bunch of extensions first. It should look like that i guess.

Via's output seemed more detailed though, according to it, it fails with this: 'vkEnumeratePhysicalDevices ERROR: Failed to query - -3'

I don't think i own any vulkan games, i just wanted to poke around with vulkan.

Something is wrong somewhere. Run this command and post the output here.
inxi -bM
or run
glxinfo -B

Next check that your environment variables.
Check for the following two.
echo $VK_LAYER_PATH
echo $VULKAN_SDK
For me they are set this way.
VK_LAYER_PATH=/home/sr_ls_boy/src/VulkanSDK/1.0.61.1/x86_64/etc/explicit_layer.d
VULKAN_SDK=/home/sr_ls_boy/src/VulkanSDK/1.0.61.1/x86_64

What is Via?

Here are mine. The location of my libraries is custom
for me and not the same placement for other distros.

/usr/share/vulkan/icd.d/radeon_icd.x86.json

Spoiler, click me

{
"file_format_version": "1.0.0",
"ICD": {
"library_path": "/usr/lib/libvulkan_radeon.so",
"api_version": "1.0.3"
}
}

/usr/share/vulkan/icd.d/radeon_icd.x86_64.json

Spoiler, click me

{
"file_format_version": "1.0.0",
"ICD": {
"library_path": "/usr/lib64/libvulkan_radeon.so",
"api_version": "1.0.3"
}
}

Since you cannot yet compile any vulkan demos, they only free vulkan
game that I know of is Dota 2. See if you can play it.

Quoting: sr_ls_boySomething is wrong somewhere. Run this command and post the output here.
inxi -bM
or run
glxinfo -B

Next check that your environment variables.
Check for the following two.
echo $VK_LAYER_PATH
echo $VULKAN_SDK
For me they are set this way.
VK_LAYER_PATH=/home/sr_ls_boy/src/VulkanSDK/1.0.61.1/x86_64/etc/explicit_layer.d
VULKAN_SDK=/home/sr_ls_boy/src/VulkanSDK/1.0.61.1/x86_64

What is Via?

I can compile all of the demos, compiling and linking are not the issue, but actually running them. VIA is part of the SDK tools to check installation.

re your last post: my libraries and json files are exactly the same place, standard place debian instals it.
for me the mentioned variables are set by sourcing env-setup.sh, they point to my local installation.

re mirv: i have the vulkan runtime lib installed via apt. Version is testings' (1.0.61.1+dfsg1-1).

edit: added the outputs below

glxinfo -B
name of display: :0
display: :0  screen: 0
direct rendering: Yes
Extended renderer info (GLX_MESA_query_renderer):
    Vendor: X.Org (0x1002)
    Device: AMD PITCAIRN (DRM 2.50.0 / 4.14.0-2-amd64, LLVM 5.0.0) (0x6810)
    Version: 17.2.5
    Accelerated: yes
    Video memory: 2048MB
    Unified memory: no
    Preferred profile: core (0x1)
    Max core profile version: 4.5
    Max compat profile version: 3.0
    Max GLES1 profile version: 1.1
    Max GLES[23] profile version: 3.1
OpenGL vendor string: X.Org
OpenGL renderer string: AMD PITCAIRN (DRM 2.50.0 / 4.14.0-2-amd64, LLVM 5.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 17.2.5
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

OpenGL version string: 3.0 Mesa 17.2.5
OpenGL shading language version string: 1.30
OpenGL context flags: (none)

OpenGL ES profile version string: OpenGL ES 3.1 Mesa 17.2.5
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.10

inxi -bM
System:    Host: ghc Kernel: 4.14.0-2-amd64 x86_64 bits: 64 Desktop: KDE Plasma 5.10.5
           Distro: Debian GNU/Linux buster/sid
Machine:   Device: desktop Mobo: ASRock model: AB350 Pro4 serial: M80-A9022500181
           UEFI [Legacy]: American Megatrends v: P3.20 date: 09/05/2017
CPU:       Quad core AMD Ryzen 3 1300X (-MCP-) speed/max: 1550/3500 MHz
Graphics:  Card: Advanced Micro Devices [AMD/ATI] Curacao XT / Trinidad XT [Radeon R7 370 / R9 270X/370X]
           Display Server: x11 (X.Org 1.19.5 ) drivers: ati,radeon (unloaded: modesetting,fbdev,vesa)
           Resolution: [email protected]
           OpenGL: renderer: AMD PITCAIRN (DRM 2.50.0 / 4.14.0-2-amd64, LLVM 5.0.0) version: 4.5 Mesa 17.2.5
Network:   Card: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller driver: r8169
Drives:    HDD Total Size: 1000.2GB (27.2% used)
Info:      Processes: 226 Uptime: 12:03 Memory: 2705.2/7982.9MB Client: Shell (bash) inxi: 2.3.45

When you compile VIA, do you end up with a 32-bit executable or a 64-bit?
The first thing that comes to mind is your are missing the proper vulkan drivers
for your arch. Meaning you should check that both 32-bit and 64-bit Mesa and
vulkan drivers are installed.

I'll have to try VIA for myself.

I have a hunch that you don't have your vulkan drivers
installed at all but instead have installed the

QuotePackage libvulkan1
sid (unstable) (libs): Vulkan loader library

That matches with your installed version 1.0.61.1+dfsg1-1.
That is a loader library provided by Khronos.
link to package

That is not the radv driver. You need

QuotePackage mesa-vulkan-drivers
sid (unstable) (libs): Mesa Vulkan graphics drivers

link to debian package

That would give you the necessary
/usr/lib/x86_64-linux-gnu/libvulkan_radeon.so

No to be confused with
/usr/lib/x86_64-linux-gnu/libvulkan.so.1
/usr/lib/x86_64-linux-gnu/libvulkan.so.1.0.51
It is those two which are at version 1.0.61.1.