I went through a range of options with my Mum's decline. Nothing really helped for long enough to justify the effort, but there's always hope it will be different for you. However when the brain's ability to handle such things is failing, chances are it's failing in all sorts of other ways around the home, so more intervention is going to be needed more often anyway. Firefighting problems like this becomes a full time job and is no substitute for someone being around to help.
Mum started off with the same TV as me so I could talk her through the remote easily. This worked some of the time, but not always, because dementia laughs at logic and following instructions.
Setting up a laptop with Skype running (configured to accept my calls automatically) and the camera pointing towards the telly also helped me check remotely whether Mum was actually doing what she said or thought she was doing. It also helped when she started forgetting how to use a phone.
I then got her a simplified remote, so she didn't have access to things like accidentally swapping the input.
https://www.alzproducts.co.uk/flipp...6WC2MDjR1b5B6tMjoryCRehRoskBOFHQaAvm3EALw_wcB But Mum was unable to get used to that very well. What looks simpler to you and me may look totally different to someone with dementia.
I ended up trying an earlier version of
https://www.amazon.co.uk/dp/B07ZSG9...=3UOkX&ref_=sbx_be_s_sparkle_mcd_asin_0_title so I could control her TV when I was 200 miles away. But apart from it being a bit messy (for me!) to set up and position where its IR could see the telly & Mum wouldn't move it, by then Mum needed a lot more help, and this was peeing in the wind. I gave up work soon after because TVs were the very least of my concerns and it was either that or a care home.
Good luck, whatever you do.
I have got myself a non smart TV and i also got that remote you mentioned Andrew, very good idea to keep him out of trouble