The latest version of macOS, Monterey 12.1 is now available to users. A few days after launching the second beta Release Candidate, the final public version has been released. However, if you are not determined to install it, you should wait to read this article, because if you install it, you will have to bear in mind that you will no longer be able to use AltServer to sign apps with your Apple ID.
AltServer is one of the best and easiest ways to effortlessly download apps to your iPhone or iPad, and it is also one of the easiest ways to install jailbreak apps like Odyssey and Tauriney unc0ver. But of course, if you have installed the software update of today's macOS Monterey 12.1, it is more than likely that you will be surprised because you will not be able to use this functionality.
It seems that the Mail application when it has been updated, causes the AltServer plugin to not work, which means that users who update to the latest version of macOS as of today will not be able to use this plugin to download or re-sign applications with the Apple ID. Is it's not the first time that a software update manipulates the functionality. Last time it involved iOS and iPadOS 15.1, which required an update to properly support.
Users will be notified of the error, whenever they try to toggle the AltServer plugin from the native macOS mail app. It essentially says that the plugin is incompatible with Mail 15.0 and has been disabled until the developer can update it. Thus, in this way it will indicate that at the moment you cannot work as you have been doing. Therefore it is more than likely that if you use AltServer you will not update your Mac to the new public version of macOS Monterey.
We will have to wait for a solution to be found for it and that's when things will return to their normal course.