@magge No, I have a desktop with the only one display adapter: RTX4090.

I am experiencing the exact same TEXCOORD1 / (particle.fx or mesh.fx) compilation error on my new PC Win 11. I've tried all the standard fixes with no success: cleaning gamedata caches, windowed mode, clean reinstalls of both FA and the FAF client, driver updates, DX9 files updates, and even a clean install of Windows 10.
Symptoms:
- Game crashes during lobby initialization with the log like TS provided.
- Occasionally, the lobby loads with a "Connecting..." hang or a broken, non-interactive UI.
Note: Vanilla Supreme Commander: Forged Alliance runs perfectly fine.

The "Background Game" Workaround:
I've discovered a strange but consistent workaround: If I launch another modern game first (not every game, but e.g., Tiny Glade, Frostpunk, or X4 Foundations) and leave it running at the main menu (no need to play this game), I can Alt-Tab back to the FAF client and launch into a lobby without any crashes. Everything works perfectly as long as that other game is open... o_O
It seems like having another 3D application active forces the GPU/DirectX into a state that allows FAF to compile its shaders correctly. Hopefully, this helps others play or assists in pinning down the root cause.