GagaJo, strangely enough just this week I have been dealing with a very similar situation to that you described in your post @18:38 today.
An employer enquired of our company what their position is as they have an employee who is stating he cannot return to work from being on furlough due to long standing chest problems.
We have advised on looking deeper into the circumstance that should the employee contract Covid-19 while at work it would be without doubt an extremely serious health situation for him.
However, as an employer they could now place the employee on sick leave with the corresponding wages payment for that. Should then the Covid-19 situation persist (example, no vaccine found in the near future) the employee could then be requested to attend an employment compatibility interview. it would then be decided at that interview whether the employee's condition is such that he would never at any time in the foreseeable future be capable of carrying out his employment duties for the company without gravely endangering his health.
Should the above be found to be the case, then the employee could be released from employment with the company on the grounds of ill-health making him incompatible with the work duties he has been employed to carry out.
Obviously, there would be no entitlement to a redundancy payment to the employee as the job will still be in existence but the existing employee is incapable of performing that work.