I brought this guy in 12 days ago, former feral/semi feral. He's evolved now from throwing himself at my bedroom window, to just occasionally crying and pawing at the door or window throughout the night. I know it's normal for him to do as he adjusts, and I never plan on putting him back out, I may allow harness walks in the distant future but I'll have to trust him not to take off.

I just want to know how to keep him properly enriched in his new indoor life and make it so he has no reason to continue missing the outdoors later on. He's to the point where I allow him to look out the window during the day now, he sits on top of his cat tree and screams at the window or just looks out calmly, and earlier today I put back the bird feeder that used to be in front of the window. Maybe that'll just tempt him more but it sounded good when I did it. So far he has a bunch of toys he doesn't care about, little interest in playing, a cat tower he uses to look out the window, cat scratcher by the door which he cares about sometimes, and places to hide when he gets sick of me. I also have a window hammock that I will put up eventually but at the moment he can't be trusted lol. He will also be limited to one hallway and 4 rooms, for potentially up to a year until I move out from my allergic dad, so I worry that that will make him depressed too. I also feel bad that I can't get him another cat friend yet because he did seem to like the other outside cats (none of them reciprocated so I didn't separate him from a bonded friend or anything).

I just want to minimize his chances of spending the next year bored and depressed. I would rather that than him be outside and dead but I don't know if I'm doing enough for enrichment. Also, I am in no way pro outdoor cat or wanting to put him back out, I always wanted him inside so bad and was very happy to be able to bring him in. So i know cats don't need outside to be happy, I just feel surprisingly guilty when he cries to the point I almost understand why less educated people say "oh but i can't keep him inside, he loves outside." Hopefully he'll shut up in the next few weeks, but I want to accommodate him fairly as I'm sure he's very annoyed being in my tiny room when he used to have all of outside to himself. Also, catio is not an option at the moment because of how the house is set up.

ETA other things he has: Slow feeder for mid-day snack, multiple things for scratching and hiding, constant attention because otherwise he'll scream, short play sessions when he bothers to do it. Yes he is fixed as well, it's been like 3 weeks

My indoor kitten loves this game, pouncing from her tunnel onto these birds I have hanging in my doorways on elastic

I feel like I’ve tried EVERYTHING. This guy is still not entertained. I’ve bought him at least £1k worth of toys that he never plays with, I’ve done scavenger hunts for him which he never does and as soon as we go out he acts like he has nothing to do!! I’ve bought him a cat tree and rearranged furniture so that he has access to look out of every window in the house as well but he still seems bored when we watch him on the cameras. Is there any tips you guys have?
Thanks in advance.

EDIT: getting him a friend isn’t an option as we haven’t got enough space in the house for a second litter box/food trays.