Pretty old apple tree in the garden which produces hundreds of not-great-tasting apples every year looks like it’s in a bit of a state. I had to cut back a weird branch that had been cut before, presumably because it shot out horizontally, and there’s a ton of rot.
It’s not in danger of hitting any buildings if it ever does fall, although could maybe take out a distracted child or two if I’m lucky.
Is there anything I can do to save it?
Certified arborist here. Fruit trees are often precious, if I'm being generous. They are short lived, prone to disease, and take a lot more work than almost any other tree to keep healthy. It's not really a bad thing, just part of what they are. If there are no target and the tree isn't too big I would just let it do its thing. Yes the tree is going to fail. Yes it is dying. Enjoy it while it lasts. Now is a good time to think about replanting. Get another tree lined up and planted, by knowledgeable people please. No buried root flares or mulch volcanos. If you play your cards right you could have another tree producing by the time this one is gone.
My (dwarf) apple tree had mast years every year and I just gave it a bit of potash and water every now and then. It wasn't difficult in any shape or form. Still sad I had to leave it when I moved.
Sometimes we get really lucky and a new tree really loves where it's planted. Love to see it.