Vegan cheese is not really good, I agree.

Check out Pan ab Tomaquet, too. Or friselle. Southern Europe is full of variations of “put olive oil and veggies on bread” like artichoke cream or grilled eggplant. Pesto is also a popular topping, you can make it vegan by replacing the Parmigiano with nutritional yeast. Those Danish open faced sandwiches on rye bread are really tasty, too… Smorrebrod i think they’re called (I know there’s a couple Danish users on hb, sorry for not using your letters).

I’m more familiar with Spanish and Italian cuisine, but I’m sure Greeks, Turkish, the balkans, and all of North Africa and/or the Levant must have some bangers to put on bread. I just remembered babaganoush, too as a topping slaps.

For Latin American cuisine, cemitas are delicious: pretty much an open faced sandwich with a base of refried beans. Venezuelan arepas are good to recreate in sandwich form if you can’t get harina PAN, and you sub or just omit the non-vegan parts: there’s the Pabellón: with black beans and slices of fried sweet plantain and whatever sub you have for shredded beef, or the Domino: black beans and shredded (vegan) cheese. Or the reina pepiada: avocado and black beans, normally with shredded chicken, but you can use some spiced seitan instead.