I also encountered the issue with FT_DEVICE_UNKNOWN when I tried to run the D2xxConsoleApp sample with my FT232R T on Ubuntu 24.04. I managed to get it working with
sudo dotnet run
after building the solution. If I publish the project as a single executable, I should also run it with sudo, e.g.
sudo ./MyApp
Otherwise, I always get FT_DEVICE_UNKNOWN and can't interact with the chip. Did you find any other solutions?
You should also make sure to unload the ftdi_sio module (used for Virtual COM Port emulation) for your FTDI device before using D2XX commands, as stated in the driver installation instructions.