• Lakka.tv: A turnkey software emulation Linux distribution. Used to pool user and local storage. Also includes my other project Opera. A 3DO emulator.
• OpenMediaVault: A network attached storage (NAS) solution based on Debian Linux. They provide plugins to manage mergerfs.
• CasaOS: "A simple, easy to use, elegant open source home cloud system." Has added initial integration with mergerfs to create pools from existing filesystems.
• ZimaOS: A more commercially focused NAS OS by the authors of CasaOS at Ice Whale.

• snapraid
• rclone
  • rclone's union feature is based on mergerfs policies
• ZFS: Common to use ZFS w/ mergerfs
• UnRAID: While UnRAID has its own union filesystem it isn't uncommon to see UnRAID users leverage mergerfs given the differences in the technologies.
• For a time there were a number of Chia miners recommending mergerfs
• cloudboxes.io

mergerfs can be found in the repositories of many Linux (and maybe FreeBSD) distributions.

Note: Any non-rolling release based distro is likely to have out-of-date versions.

• Debian
• Ubuntu
• Fedora
• T2
• Alpine
• Gentoo
• Arch (AUR)
• Void
• NixOS
• Guix
• Slackware