There is Package Announcements for… package announcements 
Otherwise, you can just use Community. A recent topic posted in Community :
You probably should not post the code directly here, unless it’s a small snippet. People often use github for their projects (or an alternative such as bitbucket, gitlab, codeberg, …) and post a link here.
Regarding the question whether beginner projects are encouraged to be share here, I don’t know. People usually ask for help when something doesn’t work (which frequently happens in beginner projects), or they share things that others might find interesting (which beginner projects rarely are).