There is a problem with the randomization. It always shows posts that are each others neighbours. I have Blogger posts since 2015, and when I use the widget it always shows 3 posts from the same week in the past.
When I use Column instead of List, the thumbnail is not square (190x190). Take a look at this screenshot: https://1.bp.blogspot.com/-K94WDsMzCZ8/Xr6ZkDqmO8I/AAAAAAAAAyI/AtDpK4_GegUzHBZVWW7s2e7_vOaCohKEQCLcBGAsYHQ/s1600/screenshot.jpg
So, when I use List, the thumbnail is always perfect (190x190), but the link is not good on the picture. And when I use Column, the link is perfect on the picture, but the thumbnail is not good.
I changed now the copyright. When I unchecked it, I didn't know that was. I was afraid it was something about the pictures I use on the blog. Please help me in this. Other people can have the same problem.
Hello! Your code is great, I have only one question: is it possible to apply the link of the post for the thumbnail picture, too? The link is now working only for the title. If I click on the thumbnail, nothing happens. I chose to have only 1 one random post with a thumbnail size of 190px which is my blog sidebar size, too.