The Canon Rebel XT 350-D (and perhaps the XTi) are vintage cameras that have lack of driver compatibility, but they have two modes with separate issues.
You can use PTP mode in Windows 10, but the latest firmware still has a bug that causes permanent "Busy" status while reading the CF card.Canon Rebel XT PC Mode:
Windows XP had a 32-bit driver to connect to the camera in PC mode, but Windows 7/8/10 do not. Therefore use a Linux operating system in PC mode (works in Ubuntu 18.04).How to Switch Modes
Settings > Advanced Menu 2 > Communication > PC Connection
It's called "Normal" on the Canon 20D
BUT I noticed that when I plugged in the camera to the PC nothing popped up, so I had to use a progam like Shotwell (for Linux) or Microsoft Photos app (for Windows) to import the photos.Alternatives
You can bypass the firmware and driver issues by have to using an external CF Card reader (~$20 new)