Posting this here for those who inevitably hit this snag:
You have to manually (at this point in time) update your Frame TV Software to version 1204 or greater via a USB Drive to enable AirPlay. I just set up a 50" 2022 Frame TV tonight and AirPlay was missing.
The OTA Update version available was only 1098, which did not have AirPlay support anywhere in the settings. Updating to 1204 fixed that problem. We have another 55" arriving today and I plan on confirming the same thing again.