So some thoughts that might help.
I've been on the forum over 10 years, the issue of oral thrush and not eating has come up, and most of the time once the thrush is treated, eating returns to 'normal' baseline.
The end of life care question is important, there is no good time to ask, and it's impossible to predict the end, it's better to think about it before hand than not have thought about it.
My below ramblings might not apply to every poster, but dementia is a degenerative illness.
The day my mum died she had been out of bed, sat in a chair, walking/shuffling with a frame, and joking with the GP on her weekly visit, she still knew me when I visited, and whilst her memory was shot, she could still converse about the weather. Her end of life/just in case pack had been prescribed 4 months earlier.
She took a sudden downturn, the district nurses were phoned to administer the end of life meds, and then the family were phoned. She passed away within a few hours.
The background to this is she had steadily been loosing weight since she arrived at the care home, the home gave her snacks, made sure she had foods they noticed she ate, gave her fortified drinks -substituted coffee for coffee flavoured ensure etc.
In Feb she caught covid (flu or a cold would have had the same effect), her sats plumeted, we were phoned and asked if we wanted her to go to hospital, as a family we said no. The just in case pack was prescribed, family several hours away travelled to see her, less than 24 hours later she had picked up. Just in case meds were kept as I was advised once prescribed kept whilst in date.
Prior to this the care home manager had talked to me about moving her across to the nursing home, I asked again afterwards and he said too frail to move, and better to stay with carers who knew her.
By mother's day in March she was in the dining room, enjoying fake alcohol, walking with her frame to the lounge etc,. The carers were pleased as she had eaten more than usual as they had a cooked breakfast to celebrate mother's day. Easter Sunday she wolfed down the chocolate provided. She was still losing weight.
In May I was taken to one side when visiting and told in the deputy manager's experience mum was near the end, it could be days, it could be weeks, it could be years. Her guess was 2 to 6 weeks.
A week later, mum caught a bad cold, family called to visit etc, and as in Feb, she rallied within a day or so. No need for just in case meds.
Then as detailed above, 2 weeks later she took a massive downturn, she never regained consciousness and this time district nurse called before family. She had a peaceful death.
I'm glad I knew what to expect from being on this forum, when I got the call in Feb I could help guide other family members as to what to expect. I was taken aback when I was asked if I wanted mum to go to hospital, but I also knew they wouldn't be asking if they didn't think we were at that point (she'd been to hospital previously from the care home).
It is never too early to have the conversation with the GP about end of life wishes with family when someone has dementia. I'd formulated plans a few years before we got there thanks to this forum.
I lost a son through still birth, as a result my husband and I discussed our outline funeral plans with each other. I wished I'd asked mum as when she had a dementia crisis 10 years before she finally died it was too late to ask her.