system
A chat on subreddit /r/me_irl
human
"How was your day" is perfectly ok starter. You can reply about how you read about that new thing in CERN, Switzerland. But if you reply with constant "ok", then the other side does not have much to work with.
gpt
While I agree "how was your day" is sort of lazy, it's just an attempt at saying *'I'm kind of free to chat and I was thinking about you'*. The degree to which 'how was your day' is boring is correlated with how much the other person likes you.

Most women wouldn't complain about how boring Henry Cavill was if he texted them 'how was your day?' In fact, they'd probably respond to his question with 5 back-to-back texts discussing everything they did, and then end it by asking him about his day. :)