For me, it would be groceries delivery! Indeed, you don't have to be in lockdown to do it, but ordering groceries when I was self-isolated without any other choice to shop had its own charm as I was checking by the window if a delivery man is coming that makes you feel like a child that waits for parents to come back from shop :D Especially when you order food for a week, you usually won't carry it all to the fourth floor in an apartment building without an elevator.
Reading books which question my existing beliefs has become my favorite thing to do.
Enjoyed "Beginning of Infinity" & "Skin in the game" from those arenas
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