Should my elderly relative apply for leave in-country?
UKVI has not issued specific guidance allowing an elderly relative to submit an application for further status in country – whether to extend a visit or to apply for indefinite leave to remain.
The Home Office has announced that everyone in the UK whose leave expires before 30 November 2021 can apply for exceptional assurance extending their leave if they are unable to leave the UK due to travel restrictions.
However your relative would be expected to leave as soon as they are able.