Pango Markup in Menus is not respected if submenu(s) are attached

Hello, this message follows posts that you can read on gnome.discourse, the latest:

Thanks to this last discussion, I was able to use pango markup in coded menu items (not XML).

The solution provided, is to use string instead of boolean as attribute:

g_menu_item_set_attribute (item, "use-markup", "s", "TRUE", NULL);

I noticed that it works providing that the menu item(s) do not have submenu(s) attached.

If a subemnu is attached to the menu item, then no markup is used no matter what:

g_menu_item_set_submenu (item, (GMenuModel*)create_submenu())

Not sure how relevant this is, but considering this might be a bug, I decided to open an issue here.

I also hope that this is the place to open it.

In any case, thank you for the time you will take to review this ... ... and thank you for GTK ;-)