your cat may need a little pal ... we've done some TNR and adoption work with cat colonies and some of these characters are very social and sociable, and really enjoy spending time with their mates. one of our two cats is like that ... he just loves to socialise with other cats. at our old house we fed and gave shelter to a tribe of ferals and our cat would always go out and just hang out with them at dinner time, play with and protect the kittens, etc.
our other cat is quite the opposite, but we notice that when we are away from home for a long while, even she seems glad she's not been all alone in the house, notwithstanding she maintains her grumpy attitude toward her housemate.
of late she's been super aggressive, but we hope it's just a phase.
you could try out fostering, see if your cat takes to having a houseguest.