You could try whether the EDL mode still works:
- Make sure the phone is off. (e.g. by re-seating the battery)
- Watch the syslog on your computer:
sudo dmesg -w - Press and hold both volume buttons at the same time.
- While holding the buttons plug in the USB cable to you computer.
The phone should do a short vibration and a usb device should appear:
usb 1-3: new high-speed USB device number 36 using xhci_hcd
usb 1-3: New USB device found, idVendor=05c6, idProduct=9008, bcdDevice= 0.00
usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-3: Product: QUSB__BULK
usb 1-3: Manufacturer: Qualcomm CDMA Technologies MSM
When it comes up with idProduct=9008 then the phone is in EDL mode.
See Fairphone 3 unbricking for some details on the EDL mode, which could be used to dump (userdata would still be encrypted …) or flash partitions.