Hi @phatlam - it's been a couple years since you reported the issue, but I ran into the same problem with Duplicator and MariaDB. It took me some days to figure out the solution, so I wanted to post it here in case it might help others.
The reason for the error is that MariaDB 10.6 and above do not have "utf8" in the list of supported character sets, even though it does exist as an alias to utf8mb3.
Since MariaDB doesn't support downgrading, a new server must be prepared; before installing the stack with Webinoly, run:
sudo stack -mysql-ver=10.5
After that, Duplicator packages from older servers can be successfully imported.