Is there a way to force the dark mode of Mac third-party apps that do not have it?

I am a huge fan of dark mode, and I am wondering if there is a way to have dark mode on apps that have not implemented it yet.

Yes. However, note that apps which do not natively support dark mode will likely contain elements which do not coordinate with the new theme, so doing this will be less effective than if the developer were to update their app.

1. Quit your app.
2. Determine the app's bundle identifier: grep -A 1 CFBundleIdentifier /path/to/your/application.app/Contents/Info.plist
3. defaults write BUNDLE_IDENTIFIER NSRequiresAquaSystemAppearance -bool false

where you would replace BUNDLE_IDENTIFIER with the actual value from step 2 (e.g., com.apple.TextEdit).