Unraid
Go to the Apps tab, search for Reaper, and install it. You'll find the template in Community Applications.
When you install, it'll ask which channel you want. Take Default to follow releases.
Can't find it in the search results? You can find the same template in the repository. Copy contrib/unraid/my-Reaper.xml to:
/boot/config/plugins/dockerMan/templates-user/
Add the container from the template dropdown in the Docker tab.
Ownership
The template ships with PUID 99 and PGID 100 so your appdata folder stays owned by nobody:users like the rest of Unraid expects. Keep them.
Where the data goes
One path, Reaper's own database. The default in the template puts it under your appdata share. Reaper needs no access to your media shares, so leave them unmapped.
The dev channel
Pick dev when you install to run the dev channel. Dev builds change often. Releases are the steadier channel.
You can only choose the channel during installation. To move an existing install, edit the container and change the tag at the end of the Repository field from :latest to :dev.
If you want both at once, install Reaper a second time. Pick dev, and give that one its own name, port, and appdata folder.
Next
Follow the First run steps in order. The first account that signs in claims the install, so make sure you know who's doing it.