The answer differs insurer to insurer but we’ll go out on a limb and say that most insurers do cover periods of absence due to Covid-19.
But most instances of Covid-19 last for a short period of time, so your income protection policy needs to align (your grace period, your claim period) to satisfy a claim.
What’s more relevant here is Long Covid, which we’re all learning more and more about as the weeks pass. Where Long Covid forces a significant period off work, income protection will pay in most cases - assuming medics and your employer agree. However do bear in mind that this doesn’t cover pre-existing long covid symptoms.