I use a Fuji X-T4, a,d a PI4, actually everything listed by DaveSW are the same except for:

The camera is set as follows:

2. Manual shutter, I can use all exposure time I want, no issue

In the Ekos/Indi setup screens:

4. SD Card (Save/Delete) seems to never save the image ono the SD card

Other observations:

- I use a 12V powered USB 3 hub (prevents under-voltage errors on Pi) for the Guide Camera and mount on USB 2. Hub plugs into a USB 2 port on the Pi
- Camera X-T4 using a Tetherd Tool cable (USB A - USB C) on PI on USB 3 port

- The LED on back of camera 100% identical as for the X-T3
Camera off and plugged into USB 3 = solid green
Camera plugged into USB 3 and power switched on = LED off
Exposure started = flashes alternately green and orange during normal operation
Exposure ended (saving file) = flashing orange
Exposure ended (awaiting next exposure start) = flashes alternately green and orange
Something is wrong = flashing green