Nucleus CMS's default database is MySQL. But MySQL is a bit complicated and large.
SQLite is a software library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. I note that SQLite can deal only with UTF-8.
Now we can utilize PHP's SQlite backend via PDO and this function is enabled as a default.
Here, Nucleus CMS's SQLite implementation exists, written by Katsumi Morimatsu. It's based on version 3.41.
I propose to merge this implementation into the core.