I have a second Pixel 6a that I want to flash with GrapheneOS. Tried Chromium on Fedora (with plugdev group and udev rules linked) and Vanadium and also Cromite on GrapheneOS. No Browser showed the device, even though adb shell works normally, as does usb data transfer.
I enabled OEM unlock and usb debugging, and enabled USB data transfer, where I tried to enable on that phone and on my GrapheneOS phone, both with no effect (put the filemanager popped up, showing the files of the other device).
Using the official usb-c to usb-c cable that came with the phone.