Two old HP thin client PCs configured as 4TB SFTP file servers using vsftpd on Debian. Each one uses software RAID 1 with both an NVMe and SATA SSD internally, and are in two separate locations with a cron job which syncs one to the other every 24 hours.
People who actually know what they are doing will probably find this silly, but I had fun and learned a lot setting it up.