Oneplus One - unlock pattern and/or retrieve data

I have a OnePlus One that went dead 7 years ago with valuable photos (for me) on it. Had it repaired recently, but can't remember the pattern I used back then... Here is what I found out about the software and status of the phone: - Android 6 with Cyanogenmod (probably version 13, maybe earlier) - USB debugging disabled - bootloader is locked - not rooted - no TWRP installed I can get the phone in fastboot mode or in Recovery Mode. The options in recovery mode are: - Reboot system - Apply update - Factory Reset - Reboot recovery - Reboot to bootloader - View recovery logs All solutions I found while researching was deleting/editing a file that contains the pattern. But that would need a phone with a custom recovery, which I can't install without wiping the phone. I have a second OPO that was my brother's old phone, which I can use as a testbed to not lose all my data on the other one. One thing I tried with the second phone was to do a hard reset, root it and try to recover data that was deleted by the reset via a recovery software. Using Fonepaw was no success, but maybe there are different, better programs out there?