The EEA Regulations do not make special provision for people who have been disabled since they came to the UK, and people in this situation who have never worked would only be able to get PR certification if they have health insurance (as self-sufficient persons), which may well be very difficult.

However, if you have worked in the UK for two years before having to stop due to incapacity, or if your disability or illness is a result of a work place accident or occupational disease, then you could be considered as a worker for the duration and could be able to apply for PR.

You will need medical evidence, and it is a good idea to have some legal assistance if it was necessary to rely on these periods, for example, to establish a child's claim to citizenship.

Unfortunately, there doesn't seem to be any provision for people who were students and had to stop due to disability.

Not having worked due to disability does not affect applications for settled status, which is based purely on residence.