Undiagnosed diabetes (and diabetes generally) are linked to gangrene. There is much more undiagnosed diabetes (and uncontrolled diabetes) in India than elsewhere in the world.
In addition to this one of India's problems is the ratio of doctors/nurses to patients. So even if you are getting hospital care, the standard of it maynot be that good and things are more likely to go untreated until they reach a critical stage.
So gangrene isn't something I'd be concerned about in the uk. Its possible but there are lots of reasons why its unlikely to get to that stage.
As for hearing loss. Its possible with ordinary head colds and flu. The key is to get any kind of infection seen to early and not to ignore ear infections.
Getting worked over this because there was a story in the newspaper shows a marked lack of understanding of comparitive risk and underlying causes of health issues (whether they are related to covid or not).