system
A chat on subreddit /r/me_irl
human
I will say the only exception for this is when I have to reach out to a friend or relative I haven't talked to in like years and mostly just want to catch up, without something specific to ask them
gpt
Normally I still try to give them *some* prompt to respond to; I know I personally hate responding to completely open-ended stuff like "hi" personally so I try not to put that on others. 

I'll normally ask some generic question like "how has work/school/relationship/hobby been going lately" so they have some jumping off point if they want to chat with me but lack the emotional energy to lead the conversation.