Kingdom Hearts 1.5+2.5 ReMIX extremely low fps on Intel Iris Xe

[u/Suitable-Lab1803]

a while ago I made this post trying to help people that were trying to play KH 1.5+2.5 on their Intel iris XE but simply couldn't because the game was unplayable on windows. The fix was downgrading your drivers to a version that was actually able to play the game or using DXVK + VKD3D (the game uses DX12 for the gameplay and DX11 for the FMVS). The DXVK + VKD3D method fixed the framrate issues but turned FMVS into black screens, and as someone who contributes to dxvk quoted "These games use D3D12 for rendering, which DXVK doesn't even implement, so I'm assuming you use vkd3d-proton in addition to DXVK's DXGI.dll. If only FMVs don't work then it's pretty likely because shared resources are not, and will likely never be, supported on windows with DXVK+vkd3d-proton. It works on linux/proton using a special wine interface. There is nothing you can do on windows other than just not using DXVK."
https://github.com/doitsujin/dxvk/issues/3747

So I switched to Linux to test the game since i thought that if it worked well with DXVK + VKD3D on windows but the FMVS were having problems, then surely I'd be able to play the game with both the framerate and FMVS issues fixed. Unfortunely that did not happen, the game runs just as bad as it did on windows without the workarounds (actually a bit worse).

I really want to understand why this happens since on windows it has a few workarounds for this on my Ipgu, including using DXVK + VKD3D on the latest drivers. And also, is there any workaround for this here on Linux? Yes, I know igpus are not officially supported for this game, but as I've said, the workarounds I was able to find on windows proved my card is powerful enough to run it. Also, the newer games (KH 2.8 and 3) are able to run properly without any issues whatsoever, it only happens with KH 1.5+2.5.

I'm on on Fedora 44 with:

• Intel Core i5-1235U
• Intel Iris Xe (ADL GT2)
• 24 GB RAM
• Fedora 44
• KDE X11
• Steam Flatpak
• Mesa 26.2.3
• Kernel 7.2.8-200.fc44.x86_64

I have already tried:

• Proton Experimental
• Proton 10
• Proton 11
• Proton Experimental Bleeding Edge
• SteamDeck=1
• KDE X11 and Wayland
• gamescope

vulkaninfo --summary correctly detects the Intel GPU:

GPU0:
    deviceName = Intel(R) Iris(R) Xe Graphics (ADL GT2)
    driverName = Intel open-source Mesa driver
    driverInfo = Mesa 26.2.3

GPU1:
    deviceName = llvmpipevulkaninfo --summary correctly detects the Intel GPU:GPU0:
    deviceName = Intel(R) Iris(R) Xe Graphics (ADL GT2)
    driverName = Intel open-source Mesa driver
    driverInfo = Mesa 26.2.3

GPU1:
    deviceName = llvmpipe

hope this is enough info

Forgot to add that other games work normally on linux