Setting up Wallpaper in Sonoma

For me so far, Wallpaper in Sonoma has been a hot mess. Here’s my setup: MBP M1 Pro in clamshell mode; two 27" LG monitors; four active Spaces. The “Displays have separate spaces” setting is off. I have a Photos album named “Vacations,” which has many sub-albums.

What I want is for each monitor to show a different random picture from one of the sub-albums in “Vacations” on each of the two external monitors. I don’t care whether the same two pictures are shown in all four Spaces or not.

I have tried every combination of settings in the new Wallpaper preference panel I can think of. None gives me the desired result. For one, only photos from the alphabetically first sub-album are considered. For another, when the photos update (every 15 minutes), only the two originally selected photos (from the first sub-album) are presented, but they will sometimes be presented on the other monitor (which is the only way I know the rotation period is working at all).

I have tried selecting the “Show on all Spaces” option in Wallpaper, but that seems to remove the option to have a different photo shown on each monitor. This strikes me as particularly odd since, as I said, the “Displays have separate spaces” option is off.

Haven’t been able to find any posts on other sites that address my particular set of issues, nor a comprehensive “how-to” article on using Wallpaper in Sonoma. Appreciate any insights.