Hello! Currently i work with people that have cerebral palsy and i set computers up with ubuntu on them.
While there are a few tweaks i have to make with gnome extensions to make ubuntu usable, the main one stopping us from having a fully end-user accessible installation process is gjs-osk.
If ubuntu included this keyboard instead of the built-in osk, i could minimize the use of a caregiver to turning on the computer and selecting the boot drive, handing off the installation process to someone with a touch screen monitor.
While I have no direct experience in the scenario you pose I do have an interest in accessability for elderly non technical patients in other scenarios (and in your case intermediary carers). I don’t understand why carers have to access “boot drive”. Do you mean LiveUSB?
One idea coming to mind is Cubic to customise your Ubuntu setup … installing gjs-osk and other aids. Another thought. You might also leverage launcher tool Albert with custom syntax in python extension designed for non technical carers. I type ctrl+space and up pops the Albert query form. Design your custom syntax for carer/patient.
Yeah im looking into cubic for this but also livebuild since i may end up forking ubuntu for this purpose and releasing it as its own distro. There are a few other changes i would add out of the box but gjs-osk is the only one thats absolutely necessary.
As for the liveusb, when dealing with a patient that cannot use a physical keyboard, it is nearly impossible to insert the usb and access a one time boot menu, so a caregiver would do that for them.
As another thought if you adopt rEFInd as grub manager you can custom design in rEFInd.conf an easier user interface than the usual grub.
Ive been thinking about bootloader stuff and refind might be something i look into. Thatd be nice to know more about!
rEFInd themes is easy to find (pardon the pun). And more here.
And there is also speech recognition option at stages.