Not sure if related, but I'm facing possibly the same issue in thunar 4.16.1. When opening the context menu for most ordinary files the "open with" sub-menu appears normally:
For a webp file as mentioned in this issue however it is missing:
But in addition I came across the same issue for any archive file I've tested so far, including bzip2, gzip, zip, and rar:
So the issue must extend beyond any particular file type.
This is unrelated, but I noticed another small regression. As seen in the screenshots above, the "Paste" context menu entry is visible when a file is selected. This was not the case in older releases.
Humm ... menus (besides shortcut-view) now use the same code to generate items. For "paste" I picked the behavior of the window-menu, which is to show paste insensitive in that use-case.
thunar-launcher, which creates the items on request does not know from which menu it is called. To fix this bug, we would need to inject the concrete menu-type into thunar-launcher.
Recently I added a check for tree-view: f12c1ad9 .. a bit hackish. So yes, possibly it makes sense to inject the concrete menu-type, to properly fix that. Even if it is only used for few items.