Is there a term for a rhetorical question designed initiate a conversation/small talk?

“Open door” questions?

An icebreaker.

I’d just call it a conversation starter or time filler,

@JeSuisRickSpringfield I usually associate icebreakers with engaging with someone for the first time. In this case it could be someone you speak with every day. Also icebreakers are’t always questions.

Mindless banter.

They are a type of conversation starter

They are not really rhetorical questions. When someone gives a rhetorical question, the asker does not expect an answer. If you ask your dog, “Who’s a good boy?”, you would not expect an answer even if the dog understood what you were asking.

The examples you give differ from usual conversation starters in that they allow for an anticipated short answer, if the person does not want to start a conversation.
Are you enjoying this beautiful day?
Yes I am.

You can try to force a conversation by then asking, “How are you enjoying this beautiful day?, which you could have asked in the first place.

Noise

A pick up line?

Icebreaker question?

An opening line that comedians start with to check there audience out.
A lead to other questions.