What a muddle this paper is.
They treat every instance of persisting symptoms after Covid-19 as Long covid (or Post-Covid-19 Condition). If you can't even separate out instances of obvious organ damage such as lung damage or heart valve damage, some of which were even caused by the treatments applied to the severe acute disease, how on earth can you meaningfully identify risk factors, prevalence, appropriate management and useful treatments?
Post-Covid-19 Condition as a single entity is a nonsense.
I mean, they appear to be wanting a 'single, agreed upon and accessible biomarker' to cover conditions as diverse as damage caused by ventilation treatments, damage caused by sustained low oxygen, ME/CFS, damage to heart valves, loss of taste and smell, new onset diabetes ....