We have similar issues!
I'm also not making jam this year.
I'm making compote, which I freeze for later use. This reduces volume occupied and gives indefinite shelf life.
Halve plums, remove stones and any trace of moth larvae, place in Pyrex casserole, add no water but a fair amount of sugar.
Microwave on full for long enough for plums to boil.
Stir. Allow to cool and decant into freezable boxes.