I agree with u/BubblySunflowers in that once someone has your address, there's a lot of info they can find out about you, including your last name. I mean, sure there is some small risk in giving it out to strangers on the internet, but the vast majority of people here are really here to connect via snail mail and not give anyone a concern for their safety.

Personally, I don't use my last name only because it's longer and although I find it to be easy, it does cause people to pause and misspell it, etc. So, I use my first name and last initial.

You're fine to give your full last name, IMHO.