Sure, just like today's disabled people are not left to die on the streets. Many disabled people never had careers to begin with so it is not a massive change. And you could always opt in to some form of disability insurance.
I'm talking from Euro PoV. In my country disabled people get payouts and special care regardless of their career or insurance. They definitely couldn't afford gear and care on common UBI.
If someone is disabled and never had a good career going, additional disability insurance is not an option for them.