Living in a rural area, it's relatively rare.

It's an annoying amount. Jehovah's Witnesses (they are relentless), Verizon (trying to get people to switch ISP services from Comcast), shady home security services that ask way too many probing questions, local activists seeking donations for their cause, and political campaign volunteers.

Generally if there's a knock on my door, I ignore it.

I'd say less than one per month where I live. (Not downtown city but also not rural)

While it varies a lot and I probably miss many for not being home, I see at least every month when the weather is good

• When there were younger families in the neighborhood, there were always kids looking to fundraiser in various ways to help fund kid activities. Selling Girl Scout cookies is a ver well known example but many kids activities do this
• now I mostly see home improvement solicitations, “we’re in your neighborhood doing x and we’ll give you a special deal if you do it now”. I don’t know if those are ever legit but it’s a well known scam
• election stuff. Way too much election stuff. New candidates need many signatures of support to get on a ballot. Local politicians want to become a familiar face. Activists want signatures for ballot initiatives or referendums