ah yes, I had that recently during my DB migration.
You need to add the following settings in:
50-server.cfg
in the section [mysql] add:
innodb_large_prefix=on
innodb_file_format=barracuda
innodb_file_per_table=1
# innodb-accelerators
innodb_buffer_pool_size = 512M
innodb_log_buffer_size = 32M
innodb_max_dirty_pages_pct = 90
innodb_default_row_format=dynamic
restart mariadb,
then it should work again.