Plums (the plums I have dried anyway) are too juicy to dry well. They sort of shrivel up into hard, sour skins, but I have 2 ways to preserve plums that I really like
1. Plum sauce (raw plum strained through a food mill and frozen flat in double freezer zip locks) on puff pastry, in tarts, over waffles, pancakes, ice cream or duck, chicken or pork. It’s quite delightful.
2. Roasting them very slowly with oil, sweetener and cinnamon and then freezing the somewhat leathery pieces for snacking or something like a topping over lemon curd and puffed pastry in the winter.
3. Plum oatmeal crisp. You can use a LOT of plums here, particularly for a pot luck. There is a recipe of a UK website 125 plum recipes. If you can’t find it call me and I’ll look it up. I just can’t do that while I’m on Vista.