Unity's decision to make the Editor's dark theme exclusively part of the paid Pro version is highly questionable. It's so much better to look at than the light theme that it can be considered an accessibility feature.Making the dark theme part of the Personal version has been the most requested Unity feature since the introduction of Unity Feedback. (Unity's feedback website doesn't exist anymore, but archive.org has got you covered)Sadly, Unity has a pretty good track record of not listening to it's community.It seems they don't intend to ever allow Personal users to use the dark theme.

So, allow me to introduce x64dbg

This workaround/hack should work with most Unity versions. Latest test: 2019.3.0a2 1. Download x64dbg2. Create a copy of Unity.exe3. Open the original .exe in x64dbg4. Switch to the "Symbols" tab and select the "unity.exe" Module

5. Search for the Symbol "getskinidx" and double click the highlighted result

6. Find the highlighted lines (might start with "jne" or "je")Replace the "je" with "jne" or the other way around, depending on your Unity version

7. Create a patch using the highlighted icon and choose the copy of the .exe

8. Finally replace the original .exe with the copy (or keep it as a backup)