Hi @marketlink
I asked Perplexity.ai about mild cognitive impairment and qualifying for MAID. Here is a brief summary of the information:

Key Takeaways
A person with MCI can apply for MAID if they meet all eligibility criteria, especially decisional capacity and informed consent.
The exclusion for "mental illness as a sole condition" does not generally apply to MCI, as it is considered a neurocognitive disorder, not a mental illness.
Loss of decisional capacity (as MCI progresses) would make a person ineligible for MAID.
In summary: A person with MCI may apply for MAID in Canada if they retain decisional capacity and meet all other legal requirements. If MCI progresses to dementia and capacity is lost, eligibility is lost as well.

My husband, who is a Canadian, has Alzheimer's Disease, since at least 2017, but diagnosed in 2019. He's pretty content and relies on me for everything. When he was younger, he always said he would kill himself if he got a chronic, debilitating disease, but that thought has completely left him.
His cousin in Ontario was diagnosed with MCI, now dementia, a few years ago. She's in the process of applying for MAID. I don't know if she'll qualify, and when I first heard about her decision, I had problems with it. I've come to terms with her decision though. Who am I to tell her what kind of life she must live? She has deep religious faith, and I just wish her the best, whatever happens.

I wish you and your husband the best as well.