> touching down on a portion of Antarctica claimed by Chile

It is worth pointing out that no other nation acknowledges Chile's claim to this part of Antarctica. And in fact, several other countries claim the same territory.

It doesn't make landing there a good idea, but it's not really an invasion of sovereign Chilean territory in a sane way. Chile claims an enormous portion of Antarctica which they exert absolutely 0 sovereignty over in practice: https://en.wikipedia.org/wiki/Chilean_Antarctic_Territory. In fact, two of the three US antarctic bases (Amundsen-Scott South Pole Station and Palmer station) are in their claimed territory, and I can assure you that US researchers do not ask Chile's permission to enter and leave.

You can call this a dumb stunt without giving credence to the goofy south american land claims Chile and Argentina are prone to making.

He landed near/at a Chile's base and is in Chile's custody. For purposes of this the claim is valid since Chile is able to enforce it and nobody else will oppose them doing so.

In general you are correct the claim isn't recognized, but it doesn't apply here.

He overflew Chile proper on his way into their territorial claims. So call it what you will but he filed a false flight plan with their regulatory body and he should face some consequences for it. The fact that his destination is in disputed territory doesn't mitigate any of that. The Chilean military and civilian bodies are being very lenient.