Third-party WidgetKit complications on watchOS 11 beta 5 are not appearing in the list of available complications. They have also disappeared from watch faces where they were installed. The exact same complications were working fine on earlier betas. This is happening on device, but not in simulator.
This issue may be related to FB14684253, which was fixed with the release of Xcode beta 5. However, Xcode beta 5 does not fix the issue on Apple Watch.
As a sanity check, I also tried with the Backyard Birds sample project, and the complications for that app aren't appearing on device either.
Filed as FB14689021.