This is a serious problem. We released an installer signed on a development computer running Big Sur, and we were flooded with complaints from users running macOS 10.9 through 10.11, all receiving the error that the installer's signature was invalid. We had to use a separate computer running Catalina to sign the installer, in order to make it compatible with these older operating systems. We'd like to know what Apple's plans are to fix this problem, and when we can expect this fix to be released. This has greatly complicated our build process, as well as our QA process. Thanks.