I had also difficulties on connecting my Fairphone 6 with win 11 (I was not on/e/os at this time) until I install the optional software linked to adb on windows update. Normally, it’s only needed for development but…
When you connect your phone and refresh windows update, does it purpose optional updates ?
My settings for usb on /e/os are : controlled by thies device (the phone) and File transfer.
Is it the same for you ? Otherwise, it may be your usb cable…
No, it’s security.
Since Android 6 by default there’s a notification on the phone once you connect it via USB, and from there you can set the mode to file transfer, as @piero pointed out (if this mechanism is not malfunctioning on your phone which would need investigating).
Since Android 15 by default you also get prompted for your screen unlock method (if you set any) when enabling file transfer.
I think I didn’t explain myself clearly: all options were disabled (all the buttons were greyed out), so I couldn’t change anything. Only switching to debug mode allowed me to resolve the issue. In terms of security, debug mode is certainly not the best option.
That is not a plausible answer regarding your cable. I also had problems with FP6 and cables (or maybe the port), C->C cable did not work, though it was from a past Pixel I had. Some good old A->C worked great.