I have family that has issues with grip and/or circulation --which causes other issues with capacitive touch. I found a stylus (and a nice collection of inexpensive ones too) goes a LONG way towards helping. In my non-medical opinion, I believe decades of muscle memory holding a pen/pencil helps the elderly navigate. Their hand also doesn't get in the way of their view either.

Voice control is a really amazing addition, but it may be overwhelming to recall some or most of the controls. So I would start small. I found a lot of success working with older adults and tech while just starting with small wins.

Also mind conditioning: start your day asking what the weather is like. That helps get them to feel less "funny" when using it. It becomes more casual and less embarrassing.

That said, Voice Control is excellent for granular control of UI elements and for simulating and/or obviating swipe gestures. For example, "Go Home" replaces swiping up from bottom.

Voice Control also actively listens to everything as potential input. So, if an input field is active, merely speaking will trigger speech-to-text in that field. The accuracy is sometimes startling.

On the other hand, watching video with Voice Control active will result in Voice Control suggesting available commands (because Voice Control will interpret some of the audio as invalid [or sometimes valid!] commands).

I am not (yet) touch or motor impaired, but Voice Control is a godsend for hands-free manipulation of the UI. I hope your mum finds it similarly helpful.