Samsung S7 edge - broken upgrade & circular reboot

/e/OS Devices Samsung
1

Hi!

I have a Samsung S7 Edge which worked nicely with e until recently. Since a week, the phone is continuously rebooting, probably after a failed upgrade.

What I want to do:

  1. Save as much data as possible & fresh install /e/
  2. If I can’t export the data, try to upgrade without losing the data
  3. If nothing works, factory reset & fresh install

Here is what I tried for 1 and 2 :

  • Access /e/ recovery (3.1.1)
  • Factory reset > Reset cache (nothing changed)
  • Install adb on the computer + Enable ADB. I restarted the server, the phone, the computer, but the device still appears as unauthorized when running adb devices… So I gave up on this.
  • Install an update from the recovery boot:
    • Downloaded 3.1.1 and 3.1.4 zip files from there
    • Update from external storage (SD card)
    • Fails:
      • Signature verification fails (E: footer is wrong)
      • Choose Yes,
      • Black screen (2 secs)
      • Back to recovery home, with following error:
E: Failed to chown(/storage/34F7-525E, 0, 0): Operation not permitted
E: public: 179_1 failed to create mount points: operation not permitted

I went through the forum, found various advices which I tried to apply, but since adb AND sd card strategies fail, I don’t know where to go. Any hints will be helpful!