Here is how we got Unity3d running on Fedora 25. It is not particularly hard, but is a bit of a chore. Pro-tip: Skip 5.6 beta for now. It has npm issues.
Install and Set Up Dependencies
Unity3d has a laundry list of dependencies. Most of them were already installed (possibly due to other software we use?) but a few weren't. Here are the basics.
sudo dnf install blender gimp monodevelop nodejs npm nodejs-npm* postgresql-libs postgresql
Also, you probably need to set up your npm permissions. http://bit.ly/1OFU9Xx
Set Up Directory Structure
You can put it anywhere, I think. We like our bin.
Get and Unpack the Unity3d Build
At the time of this post, 5.5.0b1 is our best option. You can of course try whatever version you like, just update this info to reflect that. No big deal. It is a rather large download, though. Keep that in mind.
sudo chmod 755 unity-editor-installer-5.5.0b1+20160830.sh
Run the editor for the first time.
The first time you run Unity, it will try to build/install all of the packages it needs and all of that. It can take a few minutes, but should not take too long.
Set Up Some Icons
If everything looks ok, you'll want to install some fancy icons for your launcher or docker. These all point to /opt/Unity, so we'll set that up.
cp ./unity-editor-icon.png ~/.local/share/icons/
cp ./unity-editor.desktop ~/.local/share/applications/
cp ./unity-monodevelop.desktop ~/.local/share/applications/
sudo ln -s ~/bin/unity-editor-5.5.0xb1Linux/ /opt/Unity