It does work if mail is active and I right click on the icon in the dock. Duh.
In the mail app if I highlight a message and select “message” the pulldown doesn’t have any SpamSieve option. The keyboard shortcut doesn’t work. Mail doesn’t seem to recognize that it is there within the app although it does work if I use the external dock icon.
Interesting. I’ve been using the pulldown option from messages on all versions up to 15.5. Evidently there was some legacy setting that was carried over that Onyx removed that caused it to go away.
“Shift command S” does work. Without the messages reminder of the correct keypress I must have been using the wrong one. So working fine now.