Restore MySQL Databases from File System

I had a running installation on a Raspberry-like computer (Odroid-XU4), but it crashed.
I reinstalled the System, but I created a full dd image before.

So now I want to restore the Data of the nextcloud Installation, but I don’t know how I can restore the mysql data (the User list, Calendar data…).

I have full access to all files of my previous Installation.
Copying the /var/lib/mysql/nextcloud folder didn’t quite work, mysql does not find the old database

Best Regards

If you have a manual mysql-dump you can play it back. Just using a snapshot of /var/lib/mysql/* often works but can cause problems (especially if the system is running during the snapshot). I didn’t have this problem, check other sources, how you can recover broken mysql setups.