What wine(s) would you substitute for sweet red vermouth?
I'd say sherry or marsala will have the closest flavor profile in terms of sweetness, with obviously some nuance of the herbal qualities of vermouth lost. But you could add some spices and herbs to make up for that (cloves, cinnamon, dried ginger, star anise, maybe bitter herbs like mugwort, which is easy to find where I am, or something like thyme or sage). See this article for a rough rundown of what might be in a typical vermouth.

That being said, fruit compotes are amenable to quite a lot of variations in alcohol. I sometimes used a white wine when making rote Grütze, a German style berry sauce/compote, but it's common to add a splash of something like cassis liqueur and fruit juice, but the one that went over the best I made with tart verjus. Brandy could work in moderation. If I went that direction, I'd use a fruit juice in roughly 90% the volume of vermouth intended and 10% in brandy.