community/gnome-passwordsafe: Copy & paste doesn't work

I use Gnome Secrets (community/gnome-passwordsafe) on Phosh/Wayland via postmarketOS edge. Recently copying a username or password and pasting it into another application (I've tested Firefox and Gedit) doesn't work. Secrets shows the "copied" message, but pasting into other applications isn't possible. The clipboard is either empty or holds a value previously copied from elsewhere. I'm not seeing any error messages from Secrets.

As far as I can tell the problem started after the gtk4.0 update to 4.8.0, with the catch that previously postmarketOS used a patched fork based on 4.6.6.

My suspicion is that Secrets and the other applications use different clipboards now, but I'm not sure how to debug it. I'm happy to provide additional information if anyone has a hint on how to get it.