So is it time to sell the house?

I would get permission from the court and sell the house using your Conservatorship. Maybe you can fib a little about the papers he sees if he has a fit, but one way or the other seems to me to be the best move.

After years of elder care adventures, Both my folks FINALLY went into assisted living in 2017 leaving me with 5 acres and a nasty rundown house full of stuff. I also had Conservatorship. No way was I going to mess around fixing the place up. It would have taken thousands of dollars and not really increased the value very much.

I was only surviving kid, 60 plus years old and 3 states away.

I cleaned out the personal belongings, paperwork, nasty stuff from the fridge, 40 trash bags from the house and garage to the dump, left the old ratty furniture and sold it as is. The land was valuable so it sold for a good price right away.

The money allowed me to keep them in a very nice place and later memory care for dad after mom died. Dad died just last month. Using the house funds I spent over $200K since 2017 for their care.

We get to a point where we can’t let the dementia over rule common sense decisions. I think you’re there.

I was made POA for a married couple friends of mine in 2013. The wife had frontal temporal dementia, the husband short term memory issues that kept him from processing the changes in his wife, who was the chief organizer in their relationship. It took me a long time to convince him it was time to move to the memory care apartment I had found for them, but when she became incontinent and started to wander at night and needed 24 hour care, I finally convinced him and they moved there in May, 2015. They were never coming back to their two bedroom condo with a two car garage. The wife lived to the end of October, 2015 as her mind was just shutting down and she could no longer swallow food.
I began going through all their stuff to decide what I should do. I had antique buyers come to buy some of the old antique furniture. I had native American friends of theirs come to take whatever other furniture they could use--for free. I moved some of their family heritage stuff--old photos, etc, to my house to eventually get to a relative. Then had the carpets cleaned, some damaged windows replaced and put it on the market. That took 2 1/2 years. Low value housing was in great demand and the second couple who saw it bought it. All the money went directly to the husband's bank account and helps pay for his costs. The day of their move, a friend took them out for breakfast in a nearby town, then to have their nails done. During this time, we were moving their furniture to their memory care apartment and arranged it just like they had it in their condo. Everything was familiar and when the reluctant-to-move husband saw his favorite recliner facing his same tv with the couch in the same place and the same pictures on the wall, he sat down with a sigh to relief and never said a word about living in a different place.
I never told him all I was doing to deal with their condo and I made sure any money I got went right to their bank account and never took a cent for myself. It was a lot easier this way and they had given me this authority, so I used it. I was retired and had the time and I loved giving this service to my friends.

Unoccupied home insurance? My homeowner's went from $1,300.00 a year to $4,500.00 a year.

Either rent the house or sell it. Why are you holding onto an unoccupied house when you know that he will never return?

You risk having the home occupied by squatters or wild animals.

With regards to your siblings, the money realized from the sale after taxes are paid is used for dad's care, correct?

Please remind them for me that it doesn't become an inheritance until the testator is dead.

"Inheritance" is an unseemly word to utter before probate.

If you can legally sell his home without him knowing, then I wouldn't tell him when you sell it. I sold my 87yo mother's home several months after taking care of it for two years. Honestly, I thought my mother would pass and then there would be no guilt in selling it. She has severe dementia and unable to walk and will never have "gotten better." If she asks about the house, I say "the house looks great." But since COVID and our brief visits, the house has never come up. I suspect it won't anymore. If you can sell it without your father's knowing, that's what I would do.

Get legal advice from an attorney and do you know if he is a candidate for hospice? The MC's that I know accept hospice patients, as long as they don't require IV's.

When my parents were no longer going to live in their house, my sister and I sold it and put the money in their trust account, from which their nursing home expenses were paid. The house was in excellent condition but not in an area in which it would be likely to appreciate in value--other properties for sale in that area take a long time to sell. The next-door bought it and is using it as a rental property. Neither my sister nor I had any desire to keep the house, because we don't live near the area nor have a desire to do so.

I figured that a house generates expenses while securities in the trust fund generate income, so it was an easy decision.

Since you write there is no chance for your dad to move back, do whatever causes the least stress for YOU.

If you have siblings, I would ask someone to take the lead on cleaning out the house. (This will need to be done eventually anyway). If you choose the fussiest/most headstrong sibling for this difficult task, there will be less fussing later (complaining that you had not completed this process and thus deprived them of quick receipt of their portion).

Home prices and interest rates are favorable now.

When we sold my mom's condo and later MIL's house it was a relief. However I was stunned both times when neighbors came on like vultures wanting the places for half price for themselves or relatives of theirs. One called me up after my mom died, and despite the fact they knew my mom and she was their next door neighbor for 2 decades, this boor could not even offer sympathy or condolence, just started right in how some in-laws of hers from out of town wanted it. Why didn't the in-laws call my realtor if they wanted it so bad? Someone my realtor found ended up buying it. Another neighbor tried to bully my realtor into "holding" the condo until they could sell theirs. My MIL's neighbor tried to tell my husband the house was worth half of what he ended up getting for it. Then when the home went up for sale someone used it to order cable equipment. All these boorish people and the maintenance of the homes was enough to want us to sell the homes. It was a relief when the properties sold.