Got a FP3 recently and manually installed /e/, downloaded the latest update yesterday but when it rebooted it said something akin to “Android cannot be found, if this message keeps appearing you may have to factory reset your phone”.
This repeated a few times, so I went into recovery mode, activated adb and connected the phone to my laptop. Unfortunately when I used ‘adb shell’ to browse the storage of the phone both /storage and /sdcard seemed to be empty (ls showed nothing).
I thought all hope was lost but then I clicked reboot in the recovery interface and the phone booted into the normal usable state, so I can at least backup all my data now before attempting to update. Let me know if I can do something to provide more useful information, but I will try to note what happens in greater detail when I try to update again.