Why would you want Cobra coverage if eligible for Medicare? Generally, Medicare coverage is better coverage and premiums are much less.

Be aware that if you go on cobra coverage when you are eligible for Medicare, it does not count as creditable coverage. In other words, having cobra when you are qualified for Medicare A or B could expose you to late Medicare enrollment penalties.

I faced that after my employer of 36 years forced me out. You can sign up for Medicare parts b & c plus drug plan before open enrollment as long as you were continuously insured up to that point. Be sure to sign up before your insurance is terminated by your employer. If you are on cobra with no employer contributions, Medicare could be more cost effective

Don’t pay for Cobra. Waste of money. Get Medicare B, supplemental and drug plan. Much more cost effective with better coverage

Was he eligible for long term insurance? Did he have it?
If he was fired after his diagnosis and they do not have other probable cause, this is illegal. I would definitely consult with a lawyer about this and if he did have long term, he would have been eligible for this which would carry him a long way.