What are some alternatives?
When comparing FileZilla Server and FileZilla, you can also consider the following products
vsftpd - Very secure FTP Daemon, a secure, fast FTP server for UNIX systems, including Linux.
Cyberduck - A libre FTP, SFTP, WebDAV, S3, Backblaze B2, Azure & OpenStack Swift browser.
ProFTPD - The Official ProFTPD web site. ProFTPD is a high-performance, extremely configurable, and most of all a secure FTP server, featuring Apache-like configuration and blazing performance.
Beyond Compare - Beyond Compare allows you to compare files and folders.
Serv-U FTP Server - FTP server software
PuTTY - Popular free terminal application. Mostly used as an SSH client.