As I mentioned last year, when Sequoia 15.3 was introduced, it caused issues with some apps and you had to use a codesign command in Terminal to fix that. I referenced the MacRumors link above which had other scripts as well for newer iTunes versions. While it’s not difficult to accomplish that, thankfully the Retroactive app author Shawn Cormierty has updated the previously discontinued version 2 to version 3. This version seems to handle the codesigning issues as the iTunes installs work easily. You do have to give permission for Retroactive 3 to run in the Privacy and Security settings.
Keep in mind that Intel apps will not work past Golden Gate OS27 so this only helps if you’re going to stay on that version or another previous one. I still use Sequoia mostly but also have a Golden Gate partition for experimentation. I have found that iTunes 12.6.5 works the best so far as my favorite version 10.7 is still not working properly but that started with Tahoe as I referenced earlier: