How do I help my dad, who hasn’t left the house in 2 years because of his severe ADHD & depression?

The end of 2019 my dads mom passed away and at the beginning of 2020 my stepmom left my dad. Now they had been fighting for a while but when she left things just took a major turn. He has severe ADHD and won’t even say he has it but if you observed his behavior for 2 minutes, you would be able to tell he has it. My step mom and dad were together upwards of 6-7 years and she did absolutely everything for him that wasn’t work: make every meal for him, cook, wash their clothes etc. but when she left that was all ripped from underneath him and he couldn’t “fend” for himself. Even simple meals like ravioli. Now it’s not as bad the 2 years later and he’s able to make his own food and it’s easier to get outve bed from all the grief and depression of what he’s been through. But he can’t keep the house clean OR organized. He’s a VERY smart man so he spends his time working on batteries and there electrical current and making cool more efficient gadgets for himself, but it’s so all over the place, you have to step over a lot of stuff when you go to his house. He’s not a hoarder but it kinda would seem like it cuz he doesn’t clean. And he has own specific way of doing things sometimes that he thinks actually works faster and better but really it would just be easier to do it the normal way. Like with dishes, he doesn’t like to wash them in the sink so he puts them all in a tub to soak and then spray off but that doesn’t even get them clean. Or with laundry detergent, he’ll make his own mixture of it and say it’s better. Or mopping. He uses a squeegee and soap and water but DOESNT clean the part where all the dirty water collects. So he’ll “clean” the floor but you’ll see some sections that are dried and pure dark brown nasty stuff that collected from the floor. One thing: he loves the internet and phones but has such trouble texting or calling me and my sister but then gets a lil upset when we don’t contact him. Basically he’s all alone in this dirty house with little food, working on whatever his ADHD brain finds interesting, trying to keep himself busy until life gets better and I don’t know how to help him. I get food for him, everything he’ll need for a while, I’ll clean when I go over so he can have semi better living conditions. But he gets frustrated when I clean cause it’s “moving” so much stuff and he doesn’t really like that. He has pretty bad anger issues and talks really fast and a lot of time will talk so much and fast he won’t hear or care what you said because he’s talking. And it’s so sad cuz he’s only like that cuz no one comes to visit him often so when someone is there he just rambled bcuz he’s excited. He’s like a kid and I just want to help him but it’s too much for me to handle. And this is the kicker: when his mom died she left all her stuff in his name, like stocks and stuff that has monetary value he can have. So like if he were to get all that he could start helping himself again, he just doesn’t know how. To reiterate: my ADHD dad is stuck in his own house with barely anything to do or eat and I can only visit and help so often, he has a will with money sitting in it for him, but I don’t know how to help.