Apple might have had a change of heart, iTunes 12.6.5.3 is working in 10.15.4 Beta 3 (19E242d).
I used this script
Code:
set theDMG to choose file with prompt "Please select iTunes dmg file:" of type {"dmg"}
do shell script "hdiutil mount " & quoted form of POSIX path of theDMG
do shell script "pkgutil --expand /Volumes/iTunes/Install\\ iTunes.pkg ~/tmp"
do shell script "hdiutil unmount /Volumes/iTunes/"
do shell script "cd ~/tmp/iTunesX.pkg;" & "cat Payload | gunzip -dc |cpio -i;" & "ditto ~/tmp/iTunesX.pkg/Applications/iTunes.app ~/tmp/iTunes.app;"
do shell script "plutil -replace CFBundleGetInfoString -string 'iTunes 13.6.5.3' ~/tmp/iTunes.app/Contents/Info.plist"
do shell script "plutil -replace CFBundleShortVersionString -string 13.6.5 ~/tmp/iTunes.app/Contents/Info.plist"
do shell script "plutil -replace CFBundleVersion -string 13.6.5 ~/tmp/iTunes.app/Contents/Info.plist"
do shell script "ditto ~/tmp/iTunes.app /Applications/iTunes.app"
do shell script "touch /Applications/iTunes.app"
do shell script "rm -rf ~/tmp"
do shell script "open -a /Applications/iTunes.app"
After having problems with the Retroactive solution to installing iTunes on Catalina (e.g., not being able to import songs by double clicking on them from Finder), I used a modified version of your above script on the iTunes 12.9.5 app (taken from Retroactive's iTunes launcher container app) to get that to launch by itself (without being contained inside of Retroactive's iTunes launcher container app). This worked great, but I am not able to get AppleScripts working: AppleScripts run great from Script Editor.app, but fail to even ask for automation permission when run as standalone application or from another script launcher (e.g., BetterTouchTool). Any idea how to fix this? Is there something else I need to modify in iTunes to get this last feature to work correctly?
Edit: Using the modified version of your above script that I mentioned above, I patched the iTunes app within Retroactive's iTunes launcher container app. Now AppleScript apps ask for the proper permission required to work. Unfortunately, fixing this problem broke something with keychains, because now iTunes refuses to remember the passwords for any of AirPlay speakers. I may just downgrade to Mojave. I'm so sick of Music.app's crummy search and the fact that you can't open an album within the album view anymore.
Edit2: I'm stubborn (it might be more just laziness preventing me from downgrading to Mojave) and I found a way to get my computer to store the AirPlay speaker passwords in a way that my Frankenstein's iTunes can use them. Instead of connecting to the speaker through iTunes, which for some reason can't write to Keychain Access, if you connect to the speaker through the system audio (System Preferences > Sound > Output, select AirPlay speaker) this will write the password in Keychain Access (and then iTunes will be able to read it from there without prompting you every time). I'm not sure if anyone will ever have this problem, but I'm sharing the solution here so it shows up by Google search. Thanks for joining me on this journey.