I recently decided to replace the SD card in my Raspberry Pi and reinstall the system. Without any special backups in place, I turned to rsync to duplicate /var/lib/docker with all my containers, including Nextcloud.
Step #1: I mounted an external hard drive to /mnt/temp.
Step #2: I used rsync to copy the data to /mnt/tmp. See the difference?
Step #3: I reformatted the SD card.
Step #4: I realized my mistake.
Moral: no one is immune to their own stupidity 😂
You can always try professional data recovery services. It just depends on how much the data is worth to you.
And how much time you want to put into not getting scammed.