Spray some coyote or cougar urine at the yard border. You can buy these urine sprays online, just google it.
Now I did see (online) that.
It’s called Shake-away. Or something like that.
That will just attract coyotes or cougars to come over and eat the cat!
Well, I guess that could solve the problem as well!
My indoor/outdoor cat loves to play with local foxes (that I unfortunately attracted with foxP).
But I am holding my breath that the local coyotes I hear almost every night won’t sneak up on him!