Find.Commerce is not for Commerce Manager

I’ve seen this more than once, and this can be quite tiresome to fix the problem(s) after that. So here the TL;DR: If you are installing Find.Commerce to Commerce Manager, you are doing it wrong.

You’ll probably end up in the error like this

While loading .NET types from "EPiServer.Find.UI" the following error(s) was reported:

     - System.IO.FileNotFoundException: Could not load file or assembly 'EPiServer.Cms.Shell.UI, Version=9.3.8.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7' or one of its dependencies. The system cannot find the file specified.
File name: 'EPiServer.Cms.Shell.UI, Version=9.3.8.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7'

=== Pre-bind state information ===
LOG: DisplayName = EPiServer.Cms.Shell.UI, Version=9.3.8.0, Culture=neutral, PublicKeyToken=8fe83dea738b45b7
 (Fully-specified)
LOG: Appbase = file:///C:/EPiServer/FindSearchProvider/backend/
LOG: Initial PrivatePath = C:\EPiServer\FindSearchProvider\backend\bin
Calling assembly : EPiServer.Find.UI, Version=12.0.0.4448, Culture=neutral, PublicKeyToken=8fe83dea738b45b7.

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