I had tried to install on fedora closely following all instructions(no flatpaks, flashing non root, etc) to no avail. I tried changing browsers(brave, chormium), changing cables, nothing. I did the udev rules thing by doing sudo dnf install -y android-tools. The error was:
Error: Failed to execute 'open' on 'USBDevice': Access denied.

What fixed it was simply using a different system. I used my windows 11 system and it worked flawlessly to the tee.

Funny thing is I remember flashing a different phone with graphene just couple months ago using this fedora system. I had encountered difficulties even back then, but swapping cables made it work.

    Nesurfer091 Be sure that you are using non flatpak version. Forgor what fedora is using. If i good remember you need to Type dnf install chromium...

      My Fedora laptop had similar issue. It ended up being my cable and plugging in to the right port. Try all the cables you have. IF you have a windows machine or brave enough to carve up a little windows partition, might be worth it.

      I often flash on Fedora or Arch Linux and the only issue I have is the /tmp dir, which is easy to solve, by issuing the following command on the unzipped GrapheneOS folder:

      TMPDIR="/home/$USER/tmp/" ./flash-all.sh

      Please refer to the below link to solve any issues regarding adb and fastboot (android-tools) on Fedora. These instructions can be used in any Linux distribution. It envolves creating a group for adb (adbusers) and adding yourself to it. It also has a custom rules file for udev.

      https://discussion.fedoraproject.org/t/how-to-use-adb-android-debugging-bridge-on-silverblue/2475/2

      Cheers,