Can 2 instances of Nextcloud share the same database?

In a dual-boot Linux local environment, is it possible to install Nextcloud 10/11 so that both instances use the same database?

Long version: I have Linux Mint 17.3 installed and it has Nextcloud 10 set up in the OS under a LAMPstack and syncing with Android smartphone and Thunderbird. I will migrate to Mint 18.1 but it will take time, and I would like to have a seamless/unique Nextcloud experience which ever OS I boot during the transfer time.

Not directly. For the data-folder there is no problem. The database, you could export a db-dump on shutdown and import the dump on startup of each system.
There are folder where the database stores it’s data, but I wouldn’t interfere with that directly, even if the system is shutdown, the server versions are different.