Asymptomatic also.

I have seen so many people with happy hypoxia

Yes there's probability, but In most of the cases other symptoms present but develop Very late in the course and sudden drop in O2 happens,this is one of the cause in lot of deaths in covid. How to prevent Happy Hypoxia? Aside from regularly monitoring oxygen saturation levels using an oximeter, one can look out for manifest symptoms such as discolouration of skin and lips and unnecessary profuse sweating to identify happy hypoxia. In case the oxygen saturation level drops below 90 percent, the patient must be taken to a hospital immediately.