Both iOS 15 and macOS Monterey are now available as part of Apple’s public beta program, but users who install them may find themselves with notes that are inaccessible to other devices. In fact, any note written with Apple’s betas may just vanish, rendering them unusable on some devices.
The problem appears to be tied to the updated Notes applications’ new functionality. @ mentioning and tagging are now supported, which were not available in previous releases.
Apple, on the other hand, appears to have made some arrangements in this regard. It’s worth noting that notes affected by this can be opened on iOS 14.5, iPadOS 14.5, and macOS 11.3 and later, so keep that in mind. Those who have older versions of the software on their devices, on the other hand, will be out of luck.
To minimize the issue, those affected should update to the newest stable versions of iOS, iPadOS, and macOS, or go all-in on the betas if they’re feeling particularly daring. However, I wouldn’t suggest it, and I’d always advise against putting beta software on devices that you rely on to function properly.