Interviewing while employed, I’ll happily give my “I’m not considering anything lower than <this>” number in the first 15 minutes of discussion. I’m not interested in spending more time without general alignment on that.
The few times early on that I didn’t do that, it was a giant waste of time.
If I was interviewing from a position where I needed a job soon, I would be less inclined to be that upfront, of course.
Never (ever) respond to this question early in the process. The company is just collecting market data.
Tell them that the salary should be negotiated at the end if the process is successful.
If they tell you "but we need this to make sure we're not wasting your time and ours", tell them "well give me a range for what you can do and I'll tell you if you're wasting my time"
I've always said "I'm more interested in finding the right role, than I am in the salary, and I am sure we can come to an agreement if we feel it's a good fit". If they push further than that, I ask what sort of range they are looking at to make sure we're broadly aligned and not wasting each others time.
So I am left thinking they are just collecting salary metrics for the position.