shazzbat wrote:
Our victoria plum tree has so many fruit this year that three of the
biggest branches have snapped under the weight.

Next year, remove half the fruit to avoid serious tree damage.

The plums are still 99%
green.

Lucky you - the squirrels stole all ours between Friday and Sunday. :-(

Now they're off the tree, will they ripen? And if they don't, is
there anything we can do with them?

Not that I'm aware of except make green plum jam.