As an older comment mention, they can easily add an delay that makes it work without an connection only for the duration in which an return is possible.

It is very hard to win against hostile design.

I agree with you it's hard to win against hostile design but there are options for now.

If it stops working after return period I call under warranty that it stopped working (2 years), they are forced to fix the issue.

Explain the issue, explain you cannot connect to the internet.

If it doesn't work, forward the whole info to the customer protection bureau if you're in the EU.

Edit: I will test this out by setting a date far in the future when I buy new equipment (will also hopefully cause SSL failures due to expired certificates internally in the firmware)

This would be a known defect under EU warranty law, which means once it kicks in, you can get a full refund if you want to.

They can try and fix it 3 times then you get your money back.

That would easily cause lawsuits as it is clear that the other party is doing that solely to cheat against law.