Point in time recovery with mariabackup I have a full backup dir and a bunch of hourly (incremental) backup directories taken with mariabackup, which is a port of the XtraBackup. 

How does one restore the MariaDB up to a specific minute (or second)? The general form applies all events within the incremental snapshot to the base, but what if we need to be more granular than that? I was hoping to be able to set an upper bound on the LSN or datetime.

Ref: https://mariadb.com/kb/en/library/incremental-backup-and-restore-with-mariabackup/
With a full backup you can only restore to the point in time where the backup was taken.

With a incremental backup you can only restore to the point in time where the backup was taken, but you also need the full backup on which the incremental is based upon.

If you want a true point in time recovery, you have to enable the binary log (as described here). 
In a restore scenario, you would recover a full/incremental backup and then rollforward to your point in time usinge the 'mysqlbinlog' command as described here.