The reason it's so hard to get this game to run with Proton is, ONCE AGAIN, the useless launcher.

Here's how you can defeat it:
1. Delete/rename UbisoftConnectInstaller.exe and ubiorbitapi_r2_loader.dll.

2. Create a symlink pointing to From_Dust.exe in the game's directory, and name it UbisoftConnectInstaller.exe.
   Example: ln -s From_Dust.exe "$HOME/.steam/steamapps/common/From Dust/UbisoftConnectInstaller.exe"

3. Download this tarball and extract the two files to the ../steamapps/common/From Dust/ directory, overwriting any files:
https://www.dropbox.com/scl/fi/zo112j11b3do98vnwzmqw/from_dust_ubisoft_connect_circumvent.tar.gz?rlkey=rq4w0fjtfjt68q1slq6f7lewv&dl=1

4. Set the launch options to: PROTON_FORCE_LARGE_ADDRESS_AWARE=1 PROTON_USE_WINED3D11=1 PROTON_NO_ESYNC=1 PROTON_NO_FSYNC=1 %command% (Yes, you will need the launch options. I could run the game but couldn't get past Ubisoft login without them.)

5. Done!

If you start the game and see the blue clouds on a black background screen, with that little spinning circle loading icon thing in the lower right corner, then something went wrong. Alt-F4 and try again. You'll know you did it right when it shows the main menu screen right after the Ubisoft screen.

Other problems:
The mouse cursor doesn't lock to the window, so windowed mode won't work. You have to keep it fullscreen.

The frame rate is hard locked to 30fps. There seems to be no way to increase this (yet).

Other than that, it will run great. But there are times where the FPS will drop down to like 20. But then again, From Dust is a 32-bit program so it's likely this is simply a hard limitation in the engine itself.

Enjoy!