I applied the 2023-04-06 update in which philm made changes to cryptsetup and systemd to fix the issue discussed in this thread, but unfortunately it didn’t fix the error and the nag screen persists.
For others going through this thread who also have the no such cryptodisk issue but can still boot, the solution reported as working most often seems to be the one described here or here, but running sudo grub-install does have some risks (also reported in the thread), so I’m going to find some time next week to back everything up before trying it and reporting back.