A terse, altered "Hello" is all I say. Sometimes I don't say anything. Most humans would wait a few seconds then prompt with "...Hello?", whereas bots tend to hang up after ~2s silence
They can probably ignore international calls, although only probably.
Mostly ignore unknown numbers, but if I'm expecting a call, I will pick up.
One feature that's conspicuously missing from many of these is "unknown call block" or equivalent.
Which is completely staggering to me.
I'm looking at other options, including VOIP / SIP Trunking, where it should in theory be possible to incorporate any arbitrarily complex call-screening feature(s), though Further Research is Needed.
Android / iOS phones typically have several available options for call screening. Unfortunately they include numerous other issues and negatives.
Sigh.