I entered in December 2021 and bought a travel insurance policy that mentions COVID coverage. At that time United Airlines required me to upload the policy to be declared Travel Ready (and skip departure USA airport documentation check). Nobody in Argentina asked for it, but it was attached to the Declaracion Juridica and they looked at that.
In April United no longer required the insurance certificate by provided to be declared travel ready but I got it anyway. Nobody in the USA or Argentina asked for it at any time.
At the end of May 2022 (last month) I went through Ezeiza again, and this I time did not have my insurance certificate ready to go, my papers were mixed up and I had been travelling for 33 hours (including long flight delay) and was semi-goofy in the head. I remember that the English version of the form just said I have insurance that covers COVID, which is true even without travel insurance so I felt kind of dumb buying the insurance. [If I get sick and have medical expenses, they are covered by my regular insurer, subject to the insurance policy deductible. But they would not necessarily cover hotel isolation costs, which is the point of the the travel insurance. Earlier in COVID, if you got sick as a tourist, I think you got locked up in a government supervised hotel. You are not required to go into hotel isolation anymore, and if I get COVID I will just stay home alone. So the requirement is for insurance against nothing, more or less, but is apparently still on the books. But I wanted to be sure I was safe and I try to 'play by the rules.'] Anyway, entering this time, I was asked for my juridical form, which I showed. Then the immigration person said "insurance?" One word. I fumbled through papers (flight plans, declaration, copy of passport, older documents) and found my regular medical card, CIGNA, before my travel insurance certificate. I handed it to her. It is not a travel insurance policy and says nothing about COVID insurance or hotel costs on it, but is a bit more colorful and lengthy in text than most insurance cards for some reason. She looked at it, returned it without comment, and let me enter the country.
Go figure. We need more people to post their experiences. Anyone hear of a real problem and someone getting denied entry and sent back home without entering because of no insurance that satisfied immigration? Or would they just make you buy travel insurance on the spot, which could be done in 15 minutes with a laptop and an internet connection?