I need enrichment ideas for my cat please

My cat is bored. She needs something to do. She yells at the sky. Please let me know if you have any ideas!

She is an indoor cat. I will sometimes bring her to the front porch for a change but she wants to go in after one or two minutes. She does not seem to notice birds even within five feet of her.

She does not play. She has tons of toys but does not chase things or try to catch things. If you dangle a string near her and she bats at it twice it's a miracle. She certainly won't move for it if it's not within range of her paw. She will no longer play with balls at all. If you roll one towards her, it will hit her and she will do nothing.

She was declawed before I got her so things requiring digging things out aren't ideal.

She's older and jumping onto a bed or sofa is a big deal for her.

She has no top teeth. She will eat hard treats but doesn't chew anything. She can't chew cat grass.

She's food-motivated and underweight so she can have as much food as she likes but is a very picky eater.

There was another cat here for a while and she was NOT PLEASED. I've thought about getting her/me a kitten but that could go very badly.

She loves a cardboard box. I get her new ones often, which she likes. I take out the old ones when she no longer uses them.

Please help me make my cat's life more interesting. I worry about her getting sad.