Using the excellent investigation and instructions from Tyshawn Cormier (article here), I have replicated his work and gotten Aperture to open on Catalina.

You can follow his steps where you build everything from scratch, or you can use my approach which provides most of what you need. Note: this is untested software. No promises.

EDIT: he now has an installer that does all the work, though I have no experience with it. Also, for my steps, you will need to download Xcode (free) from the Mac App Store.

Note: If you have not installed Catalina yet, then make sure to copy the NyXAudioAnalysis.framework from /System/Library/PrivateFrameworks from your Mojave or earlier OS. It’s not present on Catalina. If you have already installed Catalina and don’t have a Mojave installation, then review the steps in the medium article to see how to extract one from a Mojave installer. Previous OS installers will also work for this.

To be able to do this, you need the following:

1. Your copy of Aperture from the Mac App Store
2. Some degree of comfort with using the Terminal
3. A Mojave install from which you can extract a necessary system framework
4. A sense of adventure and detail-oriented personality 🙂

Here are the steps:

1. Download and unzip this: Aperture For Catalina
2. Copy Aperture to the ApertureForCatalina folder
3. Right click on the Aperture copy and choose Show Package Contents
4. Go into the Contents folder
5. Replace Aperture’s Info.plist with the one you downloaded
6. Locate the NyXAudioAnalysis framework from your Mojave install (or an earlier OS, it probably doesn’t matter) (it’s located in /System/Library/PrivateFrameworks)
7. Copy the NyXAudioAnalysis into Aperture’s Frameworks directory
8. Open the Terminal app and execute the following command:

cd ~/Downloads/ApertureForCatalina

10. Execute this line:

sudo codesign --remove-signature Aperture.app

11. Execute this line in the Terminal

sudo install_name_tool -change "/Library/Frameworks/NyxAudioAnalysis.framework/Versions/A/NyxAudioAnalysis" "@executable_path/../Frameworks/NyxAudioAnalysis.framework/Versions/A/NyxAudioAnalysis" Aperture.app/Contents/Frameworks/iLifeSlideshow.framework/Versions/A/iLifeSlideshow

12. Run your first test by executing the following line:

DYLD_INSERT_LIBRARIES=ApertureFixer.framework/Versions/A/ApertureFixer Aperture.app/Contents/MacOS/Aperture

13. You may get a gatekeeper warning about an inability to check for malicious software. If so, execute this line and retry the DYLD_INSERT_LIBRARIES command.

sudo spctl --master-disable

14. If it launches, then copy the ApertureFixer.framework into Aperture’s Frameworks directory
15. Execute this line in Terminal:

sudo ./insert_dylib @executable_path/../Frameworks/ApertureFixer.framework/Versions/A/ApertureFixer Aperture.app/Contents/MacOS/Aperture --inplace

16. Test with this command in the Terminal:

./Aperture.app/Contents/MacOS/Aperture

17. Code sign it with this command:

sudo codesign -fs - Aperture.app --deep

18. If you ran ito the GateKeeper warning, then re-enable GateKeeper with this line:

sudo spctl --master-enable

You should be able to open this updated Aperture from the Finder now. You can move it into Applications if you like (I renamed my original Aperture copy before putting the patched one in.)

If you run into any failures, you can copy your Aperture installation into ApertureForCatalina and start over.

If anyone wants the source to the Fixer framework (based on the medium article), you can download it here: Framework source
Here is the source to install_dylib

Notes (including some from Tyshawn’s article):

• Video will not import or play back because that requires 32-bit code that’s no longer supported on Catalina
• I have used this very little, so I don’t know what issues or bugs might be lurking.
• This has not been tested, so have backups and don’t use it with important data.
• This will likely break again at some point in the future.