I uninstalled appimagelauncher, trashed the Obsidian appimage & .desktop, downloaded a fresh appimage, created manually a .desktop (for Rofi) and specified a keybinding using the full appimage path (class name only wouldn’t work):
bindsym $mod+o exec ~/appimages/Obsidian-1.3.7.AppImage
So in the end appimagelauncher was interfering somehow by renaming things its own way I guess (?).