Hello, so I'm experiencing the same problem as you where both Elden Ring and ds3 don't work with steam input. But I can't fix it like you say. I can't find configset_controller_ps4.vdf or anything after /templates. And could problem have to do with Linux mint or RTX 2060 because I use them too.
I fixed this issue on Arch by installing game-devices-udev from the AUR.
I was playing Elden Ring and Dark Souls III with no issues last week, and suddenly my PS4 controller stopped working in those games. Steam still saw the controller working normally in a controller test, and the controller worked in another game Beam.NG Drive without the AUR package.
Arch Linux
Kernel: 6.16.8-arch1-1
Steam Version: 1757650573
Steam Client Build Date: Fri, Sep 12 4:55 AM UTC -08:00
Nothing extracted yet.
System Info
Steam client version: Wed, Jun 19 12:39 AM UTC -08:00
Distribution: Linux Mint virginia 21.3 x86_64
Opted into Steam client beta?: No
Have you checked for system updates?: Yes
Steam Logs:
controller.txt
controller_ui.txt
GPU: NVIDIA GeForce RTX 2060
Issue
I used to play Dark Souls III and Elden Ring with controller regularly. A few weeks ago I opened up steam, booted up Dark Souls III and found out that my controller didn't work. I didn't think much of it and then tried to play Elden Ring which also had the same issue.
I started testing both games with and without Steam input. Nothing changed.
I tried reinstalling Steam. Nothing changed.
I tried deleting all the Steam files off my computer including the games. Nothing changed.
I tried opting in for the beta and retried all the steps above within the beta client. Nothing changed.
I tried contacting Steam support and they had no idea and directed me here.
Then I looked at the Steam Input Controller Layout page on a hunch. Nothing loads when I open it. I don't know what that means but it is definitely related. Every other game in my library loads the page and a layout with all the controller settings that should be there. Those just don't load anything for Dark Souls III and Elden Ring.
All of this was done using a wired PS4 controller and a wireless with dongle Xbox 360 controller. Redone all of the trobuleshooting for both controllers. And both of them used to work flawlessly before.
UPDATE
I figured out what was wrong but not how to reproduce the way the problem happened.
So in /home/user/.steam/debian-installation/steamapps/common/Steam Controller Configs/userid/config there is the configs for each type of controller you may connect. Telling Steam Input which button does what.
And in /home/user/.steam/debian-installation/controller_base/templates are the text files telling Steam Input which config file to use for each game.
It turns out that in /templates/configset_controller_xbox360.vdf and /templates/configset_controller_ps4.vdf the entries for Elden Ring and Dark Souls III were deleted. I copied what the other entries looked like and replaced the game id and controller config it with the correct ones. After which my controls worked and the Steam Input Layout page loaded normally.
Now I still don't know why the entries were deleted in the first place or why that made the Steam Input Layout page not load anything. Shouldn't I have been able to just download a new layout from official sources or community page?
I figured it out by noticing that any other computer I have did not have this issue, meaning whatever files would control Steam Input Layouts would have to be stored locally. And after looking through files and folders this is what I found.
If anyone has any clue why any of this happened please leave your input.
There are still some small issues. For example I still cannot download new layouts through the layout page. It gets stuck on "downloading" But aside from that it all works great.
Steps for reproducing this issue:
I don't know what produced the issue to begin with. But it has stayed consistent through Steam client updates, OS updates.