Need help with mom. Any advice?

Just because your mom is a hoarder and chooses to live in filth, doesn't mean that you have to live with her or care for her. She has made her bed, so now she gets to lie in it.
You are WAY to young to give up your life for hers. And your mom is WAY to young to have to be looked after, so it's time you get your own place and have your own life.
Once you have moved out please make a call to Adult Protective Services(APS)and report a vulnerable adult living by themselves. They will come out and do an assessment and take things from there.
You are NOT your mothers keeper, NOR are you responsible for her care. Period.
You deserve better and I hope you know that.

In your profile you say mom has dementia/Alzheimer's.
Is this an actual diagnosis or is something you suspect?
Collecting or hoarding things can be typical of dementia.
Do you have POA? If so and you have a diagnosis that indicates that mom is not cognizant you can place her in Memory Care.
A "nursing home" or Skilled Nursing facility would be for someone that has chronic medical condition that needs nursing or medical care on a continuous basis.
If mom is on Medicaid there are usually long waits for "Medicaid beds" with the few that come up go to people that have private paid for a year or more.
It might be possible that the sale of the house would provide income to pay for some of the Memory Care.
You really need to consult with an Elder Care Attorney.
If you do not have POA then a Guardian may have to be appointed.,
If you do not want to be Guardian then the Court will appoint one and mom would then be a "Ward of the State" . The "up side" to this is you would not have to deal with it. The "down side" is that you will have no say in where mom is placed.

Move out ASAP

Do not tell her you are leaving, and do not give her your new address. Do not tell her you've moved until you're physically in your new apartment, preferably as far from her as possible.

You are not responsible for your mother's care, especially if she does not want to be helped. Do not let one ruined life turn into two.

Save your money and move out as soon as possible. Do not tell your mother of your plans. When you move call the local Adult Protective Services office and report your mother as an adult in need of care. This situation is too much for you to handle, not your fault or your responsibility, please stop trying to fix what your mother has chosen, you simply cannot make it better. What you can do is move and build a new life for yourself. It doesn’t mean you don’t love or care for your mother, it’s actually a kindness to her to get her help the only real way you can. If your mother were healthy and had rational thinking, this is exactly what she’d want for you. Change your life and don’t look back, I wish you the best

I am so sorry but I would seek out counseling with a Licensed Social Worker in private counseling practice so you can move out and get on with your life. You will not change your Mom.
There is a book I will recommend also, by Liz Scheier it is called Never Simple and about Ms. S trying to help her mentally challenged Mom for many decades, along with the auspices of the entire city and state of New York. She was unable to help her and virtually sacrificed her life on that altar trying.
You have a life to live. You cannot choose for your Mom. If you were not there she would not have you. It is unlikely that your Mom will be able to afford a good ALF or Nursing Home. If she does, and she must become a ward of the state, then they can make that decision.
I would leave, get your job, your own place, visit and have APS check on your Mom. I would not accept POA for her, nor guardianship and would let the state make decisions for how she lives her life ongoing.
I am so dreadfully sorry for what you are going through but you didn't cause this and you can't fix it.