Make sure you follow the install instructions. You have to download the Decky-lsfg-vk.zip file and install it using decky developer options. Also have to have Lossless Scaling from steam installed. I could not get Lossless Scaling to run at all no matter what version of proton I tried. So i disabled proton compatibility altogether for Lossless Scaling. I think it just needs to be there.

I had other steam Launch Options and I couldnt get get it to work until I put the ~/lsfg right before %command%.

I also uninstalled Decky LSFG-VK with the very bottom button and reinstalled and both Lossless Scaling Installed and lsfg-vk installed turned green with a checkmark.

I also disabled every toggle and set the plugin to 2X.

Then it worked. So far the only toggle I have enabled is Performance Mode and Flow Scale is at 80%.

Hope that helps.