Reference: https://medium.com/@meness/steps-to-upgrade-mariadb-for-xampp-7924326731d3

Steps to Upgrade MariaDB for XAMPP

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Tested: Upgrading to MariaDB 10.2 for XAMPP v7.1.4

Download an installer of the latest stable version of MariaDB
Be sure all modules are stopped from the XAMPP Control Panel
Rename (xampp path)/mysql to something else (i.e. mysql-old)
Install the downloaded MariaDB to the (xampp path)/mysql
Copy the mysql-old/bin/my.ini file to mysql/bin directory
Copy all .ini and .bat files from mysql-old root to the mysql root
Copy the whole mysql-old/data/phpmyadmin directory to mysql/data
Copy the mysql-old/data/ibdata1 file to mysql/data
Run Apache and MySQL modules from the XAMPP Control Panel
If both modules started correctly, run a CMD as administrator, then enter mysql-upgrade -force -username=root -password command (If your username is different, change the root to your username, and change single dash character to double dash characters)
If above command successfully was done, restart your computer once, and start using new MariaDB ;)